Prep your pan and oven: Heat the oven to 350°F (175°C). Grease a 9x13-inch baking pan or line it with parchment, leaving overhang for easy lifting.

Mix dry ingredients: In a medium bowl, whisk 2 1/2 cups all-purpose flour, 2 teaspoons baking powder, 1/2 teaspoon baking soda, and 1/2 teaspoon fine salt. Set aside.

Cream butter and sugar: In a large bowl, beat 3/4 cup unsalted butter (softened) with 1 1/2 cups granulated sugar until light and fluffy, about 2–3 minutes.

Add eggs and flavorings: Beat in 3 large eggs, one at a time. Mix in 1 tablespoon lemon zest, 2 teaspoons vanilla extract, and 2 tablespoons fresh lemon juice. If using, add 1 tablespoon neutral oil.

Combine with buttermilk: With the mixer on low, add the dry ingredients in three parts, alternating with 1 cup buttermilk, beginning and ending with the dry mix. Mix just until combined. Do not overmix.

Spread and bake: Pour the batter into the pan and smooth the top. Bake for 25–32 minutes, or until the center springs back and a toothpick comes out clean or with a few moist crumbs.

Make the lemon glaze: In a bowl, whisk 1 1/2 to 2 cups powdered sugar with 3–4 tablespoons fresh lemon juice and a pinch of salt until smooth and pourable. Adjust thickness with more juice or sugar as needed.

Glaze while warm: Let the cake cool in the pan for 10 minutes. Poke the surface lightly with a skewer or fork. Pour the glaze over the warm cake and gently spread to the edges so it soaks in.

Cool and serve: Allow the cake to cool completely so the glaze sets. Slice into squares and serve plain or with berries and a dollop of whipped cream.