Preheat the oven to 350°F (175°C) and grease your cake pan(s).
In a large bowl, cream the butter and sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition.
Mix in the strawberry Jell-O and strawberry purée until combined.
In a separate bowl, sift together flour and baking powder.
Alternately add the dry ingredients and milk to the batter, mixing gently.
Stir in the vanilla extract, then pour batter evenly into the pans.
Bake for 30–35 minutes or until a toothpick comes out clean. Let cool before serving.