Preheat the oven to 350°F, and thoroughly grease a large (12-cup capacity) bundt pan with olive oil. Place the pan on a baking sheet.
To make the cake, whisk together the almond flour, tapioca flour, baking soda, and salt in a large bowl.
Whisk together all the wet ingredients and the lemon zest in a medium bowl or two-cup measuring cup.
Add the wet ingredients to the dry, and stir until well-combined. Transfer the batter to the prepared pan, and put the pan (along with the baking sheet that's underneath it--this is just for ease of transport) in the oven.
Bake for 20-30 minutes, until the middle is set and a toothpick comes out almost clean (a few small crumbs are okay, but no goo). Cool for about 30 minutes in the pan, then carefully run a thin knife around the inner and outer edges of the cake to loosen it. You can try to invert it onto a plate at this point if it seems loose, but it might need a little bit more cajoling. If it does, place it in the freezer for 30-40 minutes, then dip the bottom of the pan into a bowl of very hot water for about 30 seconds. Invert the cake onto a plate, and it should slide right out.