Divide the batter between the pans. The capacity of a square pan is slightly more than a round pan, so put just a little more batter in the square pans, so that all the finished cakes are the same height.
Bake the cakes for about 25-30 minutes, or until a cake tester or toothpick comes out clean.
Set the cakes on a cooling rack, covered loosely with a clean kitchen towel, and cool completely.
Strawberry Buttercream and Assembly
Prepare the strawberry buttercream. Instead of making strawberry puree, you can simply use strawberry jam.
Remove the cooled cakes from the pans. Place one of the square cakes on a cake pedestal or serving plate. Cut one of the round cakes in half, right down the middle, and place them on two sides of the square cake to form a heart.
Spread a layer of buttercream on the cut edges of the round cakes, to help them stick to the square cake.
Frost the top of the first layer of cakes with the buttercream.
Repeat the above steps with the second round cake and square cake, forming the second layer of your heart cake.
Frost the cake all over with a thin crumb coat of buttercream, then chill for 20-30 minutes. Frost all over with a final layer of buttercream, making it as smooth or swirly as you like.
Garnish with fresh strawberries and orange slices.
Notes
To make the heart shape, you'll need two 6-inch square pansand two 6-inch round pans to make a two-layer heart cake that's about 9 inches in diameter and 5 inches tall once assembled.
If you like, you could make a one-layer heart cake by baking the batter in one 8 or 9-inch square pan and one 8 or 9-inch round pan, but the assembled cake will be much larger in diameter and will need to be frosted on a large baking sheet or serving platter. Using the smaller cake pans keeps the assembled cake a more standard sized-layer cake.
After the cakes are cooled, you'll make the heart by cutting the round cakes in half right down the center. Arrange the half circles of cake against two sides of the square cake (joining them together with a little buttercream), and you'll have a heart.
Keyword Cake Decorating, Heart, High Altitude Cake, Orange, Strawberry, Valentine's Day