Preheat oven to 350 degrees Fahrenheit or 175 degrees Celsius.
Butter the sides and bottom of a 9-inch round cake pan and line the bottom with parchment paper.
In a medium bowl, combine the flours, sugar, baking powder, and salt, and whisk gently.
In a large bowl, whisk together the ricotta, eggs, vanilla extract, lemon juice, lemon zest, and olive oil until the oil is fully incorporated.
Then add the dry ingredients to the liquid ingredients and stir just until the batter comes together.
Pour the batter into the pan. Bake for 25-30 minutes, until top is golden brown and springy.
Remove cake from oven and put onto a cake rack to cool.
After 15 minutes, when cake is still warm, invert cake pan onto a plate to unmold. Remove the parchment paper, then flip right-side up again.
Sprinkle with powdered sugar to serve.
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Notes
Cake will keep at room temperature for up to 3 days in an airtight container, or can be frozen. Let it cool completely before freezing.Expert Tip: I really encourage baking with weight measurements instead of cup measurements whenever possible. You will find that your baked goods are much more consistent when the ingredients are weighed. Invest in a baking scale, and you won't regret it! When you remove the cake from the oven, it may have some cracks on the top—don't worry, the dome on the cake will fall slightly as it cools, and the cracks will virtually disappear.