Preheat your oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan. You can also line the bottom with parchment paper for extra insurance.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, cream together the softened butter and sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla extract.
Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined.
Gently fold in the lemon juice, lemon zest, and diced strawberries.
Pour the batter into the prepared pan and spread evenly. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes before inverting it onto a wire rack to cool completely.