Start by making the crumble. Put all the flour, sugar, cinnamon and salt into the bowl of a standup mixer and beat to combine with the paddle attachment. Cut the butter into half-tablespoons and drop them into the mixer and beat just until combined. Transfer to a bowl and put it in the fridge while you get on with the rest of the cake.
To that same standup mixer, cream the butter and sugars together until light and fluffy—about 5 minutes.
One at a time beat in the eggs until they’re incorporated.
Beat the ricotta and zest in until it’s evenly mixed in.
In a separate bowl, combine the baking powder, salt, and all but 2 tablespoons of the flour. Stir to combine and then beat it into the batter until it’s mostly combined, but not completely. Don’t over mix it here—just let it go for about 30 seconds or so.
Toss the blueberries with the remaining flour and, with a rubber spatula, fold into the batter until everything is completely combined and the berries are evenly distributed.
Butter and flour an 8” cake pan (though an 8” springform or 8”x8” baking dish would work). Pour the batter into the tin. Sprinkle the crumble over the top, clenching some of it in your fist and then break up slightly so you get some big crumbly bits.
Bake in the preheated oven for 45 – 50 minutes, or until a toothpick comes out clean from the center.