1. Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan and line it with parchment paper for easy removal.
2. In a large bowl, cream together the butter and sugar until light and fluffy, about 3-4 minutes. This step is essential for a light cake, so take your time!
3. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
4. In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. Gradually add these dry ingredients to the wet mixture, alternating with the sour cream. Begin and end with the flour mixture.
5. Gently fold in the diced strawberries and lemon zest, if using. Be careful not to overmix, as this could make the cake dense.
6. Pour the batter into the prepared cake pan, smoothing the top with a spatula.
7. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean. The cake should be golden brown and spring back when touched lightly.
8. Allow the cake to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.

Remember, patience is key here. Allowing the cake to cool ensures that it sets properly and makes it easier to slice.