Make the Strawberry Jam: Prepare the homemade strawberry jam a few hours ahead of time and let it cool completely before using.
Preheat & Prep Pans: Preheat oven to 350°F (175°C). Butter two 9-inch round cake pans and line the bottoms with parchment paper for easy release.
Cream Butter, Sugar & Oil: In a large mixing bowl, use a hand mixer or stand mixer to cream together the butter, sugar, and oil until light and fluffy.
Incorporate Eggs: Add eggs one at a time, mixing well after each addition. Then, whisk in the egg white.
Add Flavor: Mix in the vanilla extract and fresh strawberry jam until fully incorporated.
Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking powder, and salt.
Alternate Mixing: Slowly add the dry ingredients to the wet ingredients, alternating with the buttermilk. Mix until just combined – do not overmix.
Bake: Divide the batter evenly between the cake pans. Bake for 30-35 minutes or until a toothpick inserted in the center comes out clean.
Cool the Cakes: Let the cakes rest for 5 minutes. Run a flat knife along the edges, then flip onto plastic wrap and place in the fridge to cool completely.