1️⃣ Prep & preheat:
Preheat oven to 350 °F (175 °C). Grease and flour two 8″ round cake pans (or line with parchment).

2️⃣ Dry mix:
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.

3️⃣ Cream butter, sugar & zest:
In a large bowl or stand mixer, beat butter, sugar, and lemon zest on medium-high until light and fluffy, about 3 minutes.

4️⃣ Add eggs:
Add eggs one at a time, beating well after each addition and scraping down the bowl.

5️⃣ Alternate dry & wet:
With mixer on low, add the flour mixture in three parts, alternating with the milk (beginning and ending with flour). Mix until just combined, then stir in the lemon juice by hand.

6️⃣ Bake:
Divide batter evenly between pans. Bake 22–25 minutes, until a toothpick comes out clean. Let cool in pans 10 minutes, then invert onto wire racks.

7️⃣ Make the syrup:
In a small saucepan, combine limoncello, lemon juice, and sugar. Warm over low heat, stirring until sugar dissolves. Remove from heat.

8️⃣ Soak the layers:
Prick each cake layer all over with a skewer. Brush half the warm syrup over each layer, letting it absorb fully. Cool completely.

9️⃣ Whip the mascarpone cream:
In a chilled bowl, whip heavy cream with vanilla to soft peaks. In another bowl, beat mascarpone and powdered sugar until smooth. Gently fold whipped cream into mascarpone until just combined. Stir in lemon zest if using.

🔟 Assemble:
Place one cake layer on a serving plate. Spread about 1½ cups mascarpone cream over the top. Top with the second layer, press gently, and frost the top and sides with remaining cream.

1️⃣1️⃣ Garnish & chill:
Decorate with lemon slices, mint leaves, and extra zest. Refrigerate at least 1 hour before slicing to set.