Preheat the oven to 350 degrees and prepare a 9 inch springform pan with cooking spray or butter.
In a bowl, whisk together flour, sugar, baking powder, and salt.
In a separate bowl, combine ricotta, eggs, vanilla, and lemon zest and whisk until smooth.
Add the wet mixture to the dry along with the melted butter and mix until just combined.
Pour the batter into the prepared pan, then place it on a sheet tray.
Bake on the middle rack of the oven for 45-55 minutes or until a cake tester comes out clean.
Allow to cool for 10 minutes before removing from the pan, then transfer to a cooling rack and allow to cool completely before slicing.
