1. Prepare the Cake Layers

1. Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans, then line the bottoms with parchment paper for easy release.
2. In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
3. In a large mixing bowl, cream the softened butter and granulated sugar using a hand or stand mixer on medium speed until light and fluffy, about 2–3 minutes.
4. Add the vegetable oil and mix until combined.
5. Beat in the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract and lemon zest.
6. Reduce the mixer speed to low and alternate adding the dry ingredients and the milk, beginning and ending with the dry ingredients. Mix just until combined.
7. Add the fresh lemon juice and gently fold it into the batter. Do not overmix.
8. Divide the batter evenly between the prepared cake pans and smooth the tops with a spatula.
9. Bake for 25–30 minutes, or until a toothpick inserted in the center comes out clean.
10. Let the cakes cool in the pans for 10 minutes, then turn them out onto a wire rack to cool completely.

2. Make the Lemon Cream Filling

1. In a large mixing bowl, whip the cold heavy cream on medium-high speed until soft peaks form, about 3–4 minutes. Set aside.
2. In another bowl, beat the mascarpone cheese, powdered sugar, lemon juice, and lemon zest until smooth and creamy.
3. Gently fold the whipped cream into the mascarpone mixture in three additions, being careful not to deflate the cream. Cover and refrigerate the filling for at least 30 minutes to firm up.

3. Assemble the Cake

1. Once the cake layers are completely cooled, use a serrated knife to level the tops if necessary. This ensures the layers stack evenly.
2. Place one cake layer on a serving plate or cake stand. Spread a generous layer of the lemon cream filling evenly over the top.
3. Place the second cake layer on top, pressing gently to secure it. Spread another layer of lemon cream filling on top, or reserve some for piping decorative swirls around the edges.
4. Refrigerate the assembled cake for at least 2 hours to allow the filling to set.

4. Add the Finishing Touches

1. Before serving, dust the top of the cake with powdered sugar using a fine mesh sieve.
2. Garnish with lemon slices, twists, or fresh mint leaves for a decorative touch.

5. Serve and Enjoy

Slice the cake with a sharp knife, cleaning the blade between cuts for neat slices. Serve chilled or at room temperature.