Preheat the oven to 350˚F. Line an 8-inch round baking pan with parchment paper, then spray with nonstick cooking spray.
Add lemon zest and sugar to a large bowl. Use your fingers to massage the zest into the sugar until it’s fragrant and moist. Whisk in the lemon juice, olive oil, ricotta, eggs and vanilla until smooth.
To the same bowl, add flour, baking powder and salt. Whisk until combined. Pour batter into the prepared pan and bake for 40 to 45 minutes, or until a cake tester inserted in the center comes out clean.
Let cool for about 20 minutes, then invert to remove from the pan and cool completely. Serve dusted with powdered sugar.