Prepare the Cheesecake Layer :
1. Preheat oven to 300°F (150°C). Place a pan with 1 inch of water on the lower rack (for steam).
2. Line a 9-inch springform pan with parchment on the bottom.
3. Beat cream cheese until creamy. Add sugar, salt, and flour; mix on low until smooth.
4. Add sour cream and lemon extract; mix until just combined.
5. Beat in eggs one at a time on low speed. Do not overmix.
6. Pour batter into prepared pan and place on rack above water bath.
7. Bake for 45 minutes, or until center is mostly set with a slight jiggle.
8. Turn off oven, crack door, and let sit inside for 30 minutes.
9. Remove from oven, cool at room temp. Then freeze for 2–3 hours or refrigerate overnight.
Make the Lemon Cake Layers :
1. Preheat oven to 350°F (175°C). Grease and flour two 9×2-inch round pans, line bottoms.
2. In a medium bowl, whisk flour, baking powder, baking soda, salt, and lemon zest.
3. In a separate bowl, combine buttermilk, lemon juice, oil, and lemon extract.
4. In a large bowl, beat butter until creamy. Gradually add sugar and beat 3–5 minutes until fluffy.
5. Add eggs one at a time, mixing just until blended.
6. Alternately add dry and wet ingredients, starting and ending with dry. Mix until just combined.
7. Divide batter evenly between pans.
8. Bake for 20–24 minutes, or until toothpick comes out clean.
9. Cool in pans for 10 minutes, then transfer to wire racks to cool completely.
Make the Lemon Cream Cheese Frosting :
1. Beat butter until smooth. Add cream cheese in chunks and beat until combined.
2. Mix in lemon extract and optional zest.
3. Gradually add powdered sugar, mixing until fluffy and spreadable.
4. Tint with a small amount of yellow gel food coloring if desired.
5. Chill until needed; re-whip slightly before piping if too firm.
Assemble the Cake :
1. Place one lemon cake layer on a cake board or stand. Spread with a thin layer of frosting.
2. Carefully release cheesecake from pan. Invert it onto the cake layer, remove parchment.
3. Add a thin layer of frosting over the cheesecake.
4. Place the second lemon cake layer on top.
5. Frost the top and sides with lemon cream cheese frosting.
6. Chill the cake if layers begin to shift.
7. Decorate with piped swirls or rosettes using a piping bag and tip, if desired.