Today, I have dug deep into my vintage recipe file for this super tasty Rainbow Square. This is more of a dessert square than one that would be found on a tray of squares where each individual square could be picked up and eaten from the hand. This one is best served on a plate and eaten with a fork. It would fall into the “ooey-gooey” square category, in my opinion!
I have no idea the origin of Rainbow Square but I do believe it may pre-date the 1960s. This recipe is based on, and adapted from, one my mother used to make as a treat every summer. No clue as to why it was a summertime treat in our household but that is the only time of the year I ever recall having this square and it was always considered to be a special treat!
There are three parts to the square: The shortbread base, the filling, and the meringue topping. The shortbread base is made first and allowed to cool completely before the hot filling is added. Baking the buttery-rich shortbread crust first gives the square a stable foundation and prevents the hot filling from seeping into the base making it soggy. The shortbread base is meant to have a crisp texture in just the same way as does a shortbread cookie.
The crust can be made in a food processor or the butter can be cut into the flour and sugar by hand with the use of a wire pastry cutter. I have a smaller style food processor which I like to use for this type of base as the texture of the mixture needs to be crumbly, with pieces about pea-sized, and that is easily achieved by quick pulses of the processor. This is not a “clingy” dough and the dough will not come together in a mass as would be the case for pie pastry, for example. The crumbly mixture will appear somewhat dry and that’s the way it is supposed to be for a shortbread base for a square.
Simply pat, by hand, the crumbly mixture evenly into the prepared 8”x8” pan. Just lightly pat the mixture into place; don’t pack it in hard and solid as this will make a hard, tough crust. Docking the base with the tines of a fork before it is baked helps to reduce the possibility of the crust rising up with air pockets and gives a flatter, more even base.
The delectable filling is made with crushed pineapple and red maraschino cherries, flavored with almond and vanilla, sweetened with sugar, and thickened with cornstarch. This makes both a tasty and showy filling for the square when sandwiched in between the pale shortbread crust and the meringue. I recommend draining and blotting the cherries on paper towel before cutting them up into 3-4 pieces each and then further blotting the cut pieces with dry paper towel.
The topping is a simple meringue made with egg whites, sugar, and a pinch of cream of tartar. The egg whites may be either cold or room temperature for this recipe, whichever method you are comfortable using. For meringues that top squares such as this one, I have not noticed an appreciable difference between whipping cold or room temperature egg whites. When applying the meringue to the filling, ensure that it is spread right to the edges of the pan to seal in the filling and to help prevent the meringue from shrinking and pulling away from the sides of the pan as the meringue bakes and cools.
Rainbow Square is a delightful treat any time and also makes a wonderful dessert for afternoon tea.
[Printable recipe follows at end of post]
Rainbow Square
Ingredients:
Shortbread Base:
1 cup all-purpose flour (or equal amount of gluten-free One-to-One Baking Flour, if required)
½ cup salted butter, chopped into 1” pieces
¼ cup granulated sugar
Filling:
1 cup crushed pineapple, undrained
2/3 cup maraschino cherries, cut up and well drained (blotted on paper towel)
½ cup granulated sugar
3 tbsp + 1 tsp cornstarch mixed with 2½ tbsp maraschino cherry juice (or water)
½ tsp almond flavoring
¼ tsp pure vanilla
Meringue:
2 large egg whites
¼ cup granulated sugar
1/8 tsp cream of tartar
Method:
Shortbread Base:
Position oven rack in center of oven and preheat oven to 350°F. Grease or spray 8”x8” baking pan with non-stick cooking oil. Alternatively, line pan bottom and sides with parchment paper. Set aside.
Combine flour and sugar in bowl of food processor fitted with blade. Pulse 2-3 times to blend ingredients. Add the butter and pulse a few times, just until mixture becomes crumbly. Press mixture lightly and evenly into prepared pan. Prick crust all over with tines of fork. Bake 15-20 minutes or just until crust is set, golden, and starting to show signs of lightly tanning on the edges. Do not overbake. Cool completely on wire rack before proceeding with filling preparation.
Filling:
In medium-sized heavy-bottomed saucepan, combine pineapple, cherries, and sugar. Stir well to combine. In small bowl, mix the cornstarch with the cherry juice (or water). Whisk until smooth and stir into pineapple mixture. Heat over medium heat, stirring frequently to prevent scorching. Cook until mixture is thickened. Remove from heat and set aside while making the meringue.
Meringue:
With whisk attachment fitted on stand mixer, whip the egg whites until glossy. Add the cream of tartar then slowly add the sugar. Whip until firm, but not stiff, peaks form.
Assembly:
Preheat oven to 350°F.
Spread cooked filling over baked and cooled shortbread base. Top with meringue, ensuring meringue completely covers the filling, right to the pan edges. Bake for approximately 10-12 minutes, or just until meringue is a light golden brown.
Let square cool completely on wire cooling rack before cutting and serving. Refrigerate any leftovers.
Yield: Apx. 16 – 2” squares (or cut to desired size)
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Vintage Rainbow Square Recipe
Ingredients
Shortbread Base:
- 1 cup all-purpose flour (or equal amount of gluten-free One-to-One Baking Flour, if required)
- ½ cup salted butter, chopped into 1” pieces
- ¼ cup granulated sugar
Filling:
- 1 cup crushed pineapple, undrained
- 2/3 cup maraschino cherries, cut up and well drained (blotted on paper towel)
- ½ cup granulated sugar
- 3 tbsp + 1 tsp cornstarch mixed with 2½ tbsp maraschino cherry juice (or water)
- ½ tsp almond flavoring
- ¼ tsp pure vanilla
Meringue:
- 2 large egg whites
- ¼ cup granulated sugar
- 1/8 tsp cream of tartar
Instructions
Shortbread Base:
- Position oven rack in center of oven and preheat oven to 350°F. Grease or spray 8”x8” baking pan with non-stick cooking oil. Alternatively, line pan bottom and sides with parchment paper. Set aside.
Combine flour and sugar in bowl of food processor fitted with blade. Pulse 2-3 times to blend ingredients. Add the butter and pulse a few times, just until mixture becomes crumbly. Press mixture lightly and evenly into prepared pan. Prick crust all over with tines of fork. Bake 15-20 minutes or just until crust is set, golden, and starting to show signs of lightly tanning on the edges. Do not overbake. Cool completely on wire rack before proceeding with filling preparation.
Filling:
- In medium-sized heavy-bottomed saucepan, combine pineapple, cherries, and sugar. Stir well to combine. In small bowl, mix the cornstarch with the cherry juice (or water). Whisk until smooth and stir into pineapple mixture. Heat over medium heat, stirring frequently to prevent scorching. Cook until mixture is thickened. Remove from heat and set aside while making the meringue.
Meringue:
- With whisk attachment fitted on stand mixer, whip the egg whites until glossy. Add the cream of tartar then slowly add the sugar. Whip until firm, but not stiff, peaks form.
Assembly:
- Preheat oven to 350°F.
- Spread cooked filling over baked and cooled shortbread base. Top with meringue, ensuring meringue completely covers the filling, right to the pan edges. Bake for approximately 10-12 minutes, or just until meringue is a light golden brown.
- Let square cool completely on wire cooling rack before cutting and serving. Refrigerate any leftovers.
Recipe Notes
Yield: Apx. 16 – 2” squares (or cut to desired size)
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