A highly rated recipe for raspberry squares is raspberry crumble bars from the Food Network, which has a raspberry layer nestled between an oat-based crust and top layer. Another recipe, raspberry streusel bars, features a sugar cookie crust and a streusel top.
To make Food Network's raspberry squares, whisk together 2 1/4 cups of all-purpose flour, 1/2 cup each of granulated sugar and light brown sugar, 1 cup of rolled oats and 1/4 teaspoon of fine sea salt, and stir in 2 sticks of softened butter and 1 egg. Press all but 2 cups of the mixture into the bottom of a square baking pan. Simmer 1 quart of raspberries and 1/4 cup of water over medium heat for 10 minutes, and stir in 1 3/4 cup of sugar and 1 tablespoon of lemon juice. Once the mixture thickens, pour it over the crust, and sprinkle the remaining crumb mixture on top. Bake the bars at 350 degrees Fahrenheit for 40 to 50 minutes.
For raspberry streusel bars, mix together 1/2 cup of melted unsalted butter, 1/4 cup granulated sugar, 1 teaspoon of vanilla extract, 1/4 teaspoon of salt and 1 cup of all-purpose flour. Press the mixture into a square baking pan, and bake it at 300 F for 15 minutes. Meanwhile, mix 3/4 cup of raspberry preserves with 16 fresh raspberries. Spoon the filling over the cooked crust.
Toss 1/2 cup of old-fashioned oats and 1/4 cup of all-purpose flour with 1/3 cup of light brown sugar and 1/4 teaspoon of ground cinnamon, and cut in 1/4 cup of cold unsalted butter. Sprinkle the streusel over the filling, and bake the bars at 350 F for 30 to 35 minutes.