Preheat oven to 375F/190C. Spray a 10-inch/25 cm springform pan with non-stick spray and wrap the outside of the pan in a double thickness of aluminum foil. Place on a baking sheet and set aside..
In a small bowl, stir together the flour, salt and baking powder; set aside.
Place oil, sugar, vanilla, lemon juice and zest in a large bowl. Beat with an electric mixer at medium speed until well combined.
Beat in the eggs, one at a time, until well mixed. Now mix in the ricotta and sour cream, blending well.
Add the flour mixture and beat until just incorporated. Pour batter into the prepared pan.
Bake for 35-40 minutes, or until a toothpick inserted in the center comes out clean.
Cool completely and dust top with confectioner's (icing) sugar.