Preheat the oven to 350° F/180° C, position a rack in the middle of the oven. Prepare an 8-inch round cake pan, by greasing it with oil spray or butter and lining the bottom of the pan with parchment paper.
In a medium mixing bowl, sift flour, baking powder, and baking soda. Add salt, whisk the dry ingredients until well combined. Set aside.
In the bowl of your stand mixer fitted with the paddle attachment, beat unsalted butter and sugar on medium-high speed until light and creamy, scraping down in between, about 2-3 minutes. Or you can use an electric hand mixer/beater.
Add ricotta cheese, continue beating on medium speed until fluffy.
Add in the eggs one at a time, continue beating on medium-high speed. Scrape the sides of the bowl in between. The batter will look curdled at this point, and that is okay.
Add almond extract, lemon zest, and lemon juice. Beat on medium speed for another 30 seconds.
Add the dry ingredients and mix on the lowest possible speed until there are no more flour pockets. (DO NOT OVERMIX).
Transfer the batter to the prepared pan. Gently tap it on the counter 2-3 times to remove the air bubbles. Sprinkle some slivered almonds all over the top (optional). Bake on the middle rack for 35-40 minutes or until the toothpick inserted in the center of the cake comes out clean.
Transfer the cake to a cooling rack. Let it cool down in the pan for 15 10 minutes, then remove from the pan and cool on the rack completely.
Invert the cake gently and peel off the parchment paper. Flip it back, slice the cake, and serve!