1. Preheat oven to 350°F (175°C). Whisk together flour, baking powder, and salt.
2. In a large bowl, beat sugar, oil, eggs, egg whites, and extracts until combined. Add sour cream and beat again. Add half the flour mixture and beat just until combined. Slowly add milk and the remaining flour mixture, mixing gently without over-mixing to maintain a light texture.
3. Prepare three 8-inch cake pans by greasing and lining with parchment paper. Divide the batter evenly among pans and tap to remove air bubbles. Bake 18-22 minutes or until a toothpick comes out clean; rotate pans if needed. For two-layer cakes, bake 22-27 minutes and expect thicker layers. Cool completely in pans.
4. Mix 2½ cups sliced strawberries with the strawberry jam to macerate; set aside. Dice about ½ cup strawberries for topping.
5. For the frosting, beat cream cheese, powdered sugar, and vanilla extract until smooth. Gradually add cold heavy cream while whipping on medium speed, then increase to high speed until stiff peaks form. Keep cream chilled throughout to ensure stability.
6. Assemble by placing one cake layer on a serving plate, spreading one-third of the frosting over it, and evenly layering 1¼ cups of the macerated strawberries. Repeat for the second layer (or the middle layer if three). Frost the top and sides with remaining frosting. Decorate the center with diced or whole strawberries and optionally garnish the sides with whole strawberries.
7. Refrigerate the assembled cake until ready to serve. Bring to cool room temperature before serving for optimal flavor and texture.