Tear off a large sheet of parchment paper so that it overhangs the base of a 9-inch springform cake pan. Clip on the ring catching the paper between the ring and the base. Butter the sides and dust with flour.
Preheat the oven to 350ºF (180ºC).
Zest the lemon (just the yellow part) then squeeze the juice.
In the bowl of a stand mixer, rub the lemon zest and sugar with your fingertips until fragrant.
Add the unsalted butter and vanilla extract. Then beat using the paddle attachment on medium speed until creamy and pale - about 5 minutes.
Add eggs one at a time to the sugar and butter mixture.
Turn the stand mixer to low and add the ricotta. Beat on low until well combined.
Sieve the flour, baking powder and salt directly onto the sugar/butter/ricotta mixture using a fine mesh sieve. Alternatively, in a medium bowl, whisk flour, baking powder, and salt together to combine and remove any lumps then add to the creamed mixture.
Turn the stand mixer on low until the flour is just incorporated. Stop and scrape the sides and the bottom of the bowl to ensure all the mixture is combined.
At low speed, add the lemon juice and mix until just combined. Don’t over-mix.
Scrape the cake batter into the prepared pan and bake for 40-50 minutes or until a skewer inserted comes out clean with a few crumbs clinging. Check the cake at 40 minutes. My oven cooks unevenly, so at 40 minutes, I carefully and quickly adjust the position of the cake pan.
When baked, allow the cake to cool in the pan for 15 minutes before removing the outer ring. Carefully lift the cake off the base using and slide onto a wire rack to cool.
This cake will settle as it cools. That's perfectly normal.
Notes
Use room temperature butter. It should be soft, but not melted.
The ricotta must be quite dry. Strain ricotta if it contains excess liquid.
To measure flour: stir to lighten the flour, then spoon it into measuring cups and use a knife to level. For accuracy, use kitchen scales.
Substitutions
Butter – Use salted butter if that's all you have, but omit the extra pinch of salt
Fresh lemon juice and zest – Swap with 1 teaspoon of lemon extract or use bottled juice with a few drops of lemon oil.
Tips for Success
Line the springform base with overhanging parchment for easy transfer after baking.
Avoid overmixing, which can make the cake tough.
The batter is thick but bakes up light yet moist and dense.
Baking times vary. Check at 40 minutes and test with a skewer.