Preheat the Oven

Set your oven to 350°F (175°C).

Grease two 8-inch round cake pans with butter. Line each with parchment paper, then grease the parchment. Dust the bottom and sides with flour, tapping out any excess.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In a food processor, combine the sugar, lemon zest, and dried lavender. Process for 1 to 3 minutes, until the lavender is finely ground and both the zest and lavender are evenly distributed throughout the sugar.

In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), beat the butter, vegetable oil, and lemon-lavender sugar on medium-high speed for about 4 minutes, until the mixture is very pale, fluffy, and has nearly tripled in volume.

Beat in the eggs one at a time, making sure each is fully incorporated before adding the next. Scrape down the sides and bottom of the bowl as needed. Stir in the vanilla extract.

Add half of the flour mixture to the creamed butter mixture and mix on low speed until just combined. Pour in the milk and lemon juice, mixing again on low speed. Add the remaining flour mixture and mix until just incorporated — it’s okay if there are a few small lumps. Use a rubber spatula to scrape the bowl in between to ensure even mixing.

Divide the batter evenly between the two prepared pans. Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean. The edges should begin to pull away from the pans, and the center should spring back when gently pressed.

Let the cakes cool in the pans for 15 minutes. Then, turn them out onto a wire rack and allow them to cool completely before frosting.

Prepare the Frosting – Beat the Butter

In a stand mixer with the paddle attachment (or using a hand mixer), beat the butter on medium speed for about 2 minutes, until smooth and satiny.

Add Powdered Sugar, Milk, and Lemon Extract

Add the powdered sugar, half of the milk, and the lemon extract. Beat on medium speed until the mixture becomes light and fluffy, about 2 minutes. If needed, add more milk 1 tablespoon at a time to reach your desired frosting consistency.

Place one cake layer right-side-up on a plate or 10-inch cake board. Spread 1/2 to 1 cup of frosting evenly on top. Place the second cake layer upside-down on top to create a flat, smooth surface. Make sure the layers are centered and level.

Using an offset spatula or butter knife, spread a thin, even layer of frosting over the top and sides of the cake. This crumb coat traps any loose crumbs and helps create a clean finish for the final layer.

Refrigerate the crumb-coated cake for 20 minutes to let the frosting set. Cover the bowl of frosting in the meantime.

Once chilled, remove the cake from the fridge. Stir the frosting to smooth it out again. Apply a generous layer over the top and sides of the cake, smoothing it out with a spatula, spoon, or butter knife.

Store the finished cake in a cake saver on the counter for up to 4 days.

For leftover slices, cover them with plastic wrap on a plate.

If part of the cake has been cut, cover the exposed edges with plastic wrap or parchment paper to prevent them from drying out.