Preheat oven to 350°F (175°C). Grease a 9-inch springform pan.
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
In a large bowl, rub the sugar and lemon zest together with your fingertips until fragrant and moist.
Add the softened butter to the lemon sugar and beat until light and fluffy, about 3 minutes.
Add eggs one at a time, beating well after each addition, then mix in the vanilla extract.
Gently fold in the ricotta cheese until just combined. The batter will be thick
Transfer half the batter to the prepared springform pan, spreading it evenly.
Carefully spoon the warmed lemon marmalade over the batter, keeping it away from the edges. Use the back of a spoon to gently swirl it through the batter.
Top with the remaining batter, spreading carefully to cover the marmalade layer.
Bake for 50-55 minutes until golden and a toothpick inserted in the center comes out clean or with a few moist crumbs.
Cool in the pan for 15 minutes, then run a knife around the edge and release the springform ring. Allow to cool completely on a wire rack before dusting with powdered sugar.