Step 1: Prep Your Pan - Preheat oven to 350°F. Line a loaf pan or an 8x8-inch square pan with parchment paper and lightly grease it.
Step 2: Mix the Batter - In a stand mixer or bowl, cream the butter, oil, and sugar until light and fluffy, about 2–3 minutes. Beat in eggs one at a time, followed by lemon zest, lemon juice, sour cream, and vanilla.
Step 3: Mix Dry Ingredients - In a separate bowl, whisk together flour, baking powder, baking soda, and salt. Add dry to wet, mixing just until combined.
Step 4: Layer and Swirl - Pour half of the batter into your prepared pan. Dollop lemon curd over the top, then swirl gently with a knife. Repeat this process with the remaining batter and curd.
Step 5: Bake - Bake for 45–55 minutes, or until golden brown and a toothpick inserted into the cake (not the curd!) comes out clean. Cool completely before glazing.
Step 6: Glaze + Finish - Whisk powdered sugar and lemon juice to form a thick glaze. Drizzle over cooled cake and finish with extra zest. Optional: sprinkle the top with turbinado sugar and torch lightly for a brûléed effect.
Notes
Add a pinch of salt to your glaze to balance the sweetness and amplify the lemon.
Don’t over-swirl. Gentle swoops create pockets of curd. Over-mixing blends it in and dulls the flavor.
Room-temperature curd Cold curd clumps; let it sit out so it ribbons cleanly into the batter.
Zest before juicing. You’ll get way more flavor, and it’s much easier to handle the lemon this way.
Butter + oil combo Butter gives flavor, oil keeps the cake moist for days. Use a neutral oil like canola.
Check doneness early. This cake can dry fast. Start testing with a toothpick a few minutes before the timer ends.