Preheat the oven to 400 degrees to warm it up as a "hot box" for the pizza dough to proof. Oil an 8-inch round pan, an 8-inch cast-iron skillet, or, for a pretty presentation, a springform pan (this is what I used).
In a small bowl, mix together the lukewarm water, yeast, sugar, and gelatin; set aside.
In the bowl of a stand mixer, using the whisk attachment, mix the almond flour, starches, xanthan gum, salt, and baking powder until blended.
Add the oil, vinegar, and yeast mixture and mix until it comes together into a sticky dough that holds together.
Place the dough in the prepared pan. Press the dough across the bottom of the pan and 1 inch up the sides. Cover the pan with a towel.
Turn off the oven and place the covered pan in the warm oven to proof for a total of 30 minutes. Leave the oven door open a crack for the first 15 minutes, and then close the door for the last 15 minutes.
While the dough is proofing, cook the sausage: Remove the casings. Break the sausage meat into small pieces and brown in a skillet over medium heat. Remove with a slotted spoon and set on paper towels to drain.
After 30 minutes of proofing, remove the pan from the oven. Preheat the oven to 400 degrees.
When the oven is full preheated, remove the towel from the pan and place the pan in the oven. Prebake the crust for 5 minutes, and then remove from the oven. (But leave the oven on!)
It's time to layer on the toppings! Put the mozzarella cheese on the bottom, followed by a layer of sausage, then pour on the diced tomatoes, and top with the Parmesan cheese, if using.
Bake for 30 minutes, until the cheese has melted and the crust is golden brown.