Keep the oven at 350 degrees F (as it was for roasting the strawberries). And grease an 8-inch heart cake baking pan OR two regular 8-inch cake pan. Set aside.
In a medium bowl, add the flour, baking powder and salt. Whisk until combined. Set aside.
To the bowl of a stand-up mixer with the paddle attachment, add the butter and sugar. Beat until light and fluffy, about 2 to 3 minutes. In a measuring cup, pour in the milk, egg whites, vanilla extract or paste and reserved 1/4 cup strawberry puree (save the rest for the frosting) and whisk until combined.
Turn the mixer to low speed and, alternating between the dry ingredients and the liquid ingredients (the strawberry/egg white mixture), add the them butter/sugar mixture until the batter is relatively smooth. If you want to make it a bit more pink (it’ll probably be a light pink), add a drop of food coloring.
Pour the batter into the prepared baking pan and transfer to the oven to bake for 20 to 25 minutes, until a skewer inserted into the center comes out clean. OR, if you're using a single heart pan, add half of the batter to the pan. (We'll fill it up after we bake the first layer.)
*NOTE: You can buy two heart pans, but I bought one. So I baked this cake one layer at a time.
Allow the cake to cool in the pan for about 5 minutes and then invert onto a cooling rack and cool to room temperature. It’ll probably take a good hour. Repeat with the second layer, if needed.