Preheat your oven to 350°F / 175°C. Prebake your tart crust according to its directions.
While it bakes, you can start preparing the filling.
Once the crust is done, remove it from the oven and let it cool slightly on a wire rack.
Keep the oven on.
In a food processor or spice mill, grind 1 ½ cups of the almonds into a fine powder. Roughly chop the remaining 1 cup (240 ml) of almonds for texture.
In the bowl of a standing mixer (or a large bowl with a hand mixer), beat the eggs and sugar together on high speed until the mixture is thick, pale yellow, and has significantly increased in volume. This can take up to 10 minutes.
Gently fold in the ground almonds, chopped almonds, cinnamon, and lemon zest until just combined.
Pour the almond filling into the prebaked crust, spreading it evenly.
Bake for 30 to 45 minutes. The tart is done when the center is set and a toothpick inserted into the middle comes out clean.
Let the tart cool completely on a wire rack before removing the sides of the tart pan. Just before serving, dust generously with confectioners sugar.