For the pizza dough:
In a large mixing bowl combine the flour, salt, instant yeast and sugar. Mix well to combine. Drizzle over the olive oil and just give a quick stir.
Make a well in the middle of the flour and pour in about 1 1/2 cups of the water. Using a fork, start pulling the flour into the water until you have incorporated all the flour. If it seems too dry, add remaining water. The dough should be really sticky at this point.
Take the dough out of the bowl and place on a clean and lightly floured surface. Lightly flour your hands and start kneading the dough. Flip and knead the dough until it's soft, elastic and springs back when touched. This will take between 5 - 10 minutes.
Place the ball of dough in a large flour-dusted bowl. Cover the bowl with a damp cloth and place in a warm room for about an hour or up to two hours until the dough has doubled in size.
Now remove the dough to a flour-dusted surface and punch it down. You can either use it immediately, or keep it wrapped in plastic wrap in the fridge until required.
The rest of the pizza:
Preheat oven to 500 degrees F. Place a pizza stone or cast iron slab on the bottom rack of the oven.
Place a skillet over medium heat and add the olive oil. Add the sliced onions and give a good stir. Cook over high heat for about 3 -5 minutes until the onions are starting to brown. Reduce heat to medium and continue cooking for about 15 - 20 minutes, stirring occasionally. Note: You may need to add a splash of water to the onions as they are cooking to prevent sticking or burning. Remove from heat when done.
Place one ball of pizza dough on a lightly floured surface and press down with your hands until you have a disk. Using a rolling pin, roll the pizza base out to about 10 - 12 inches. Place the pizza base on a large sheet of parchment paper. Transfer the pizza base onto a pizza shovel or board (on top of the parchment paper)
Top the pizza with marinara sauce, oregano, caramelized onions, goats cheese, parmesan cheese and fresh spinach.
Transfer the pizza to the baking stone in the oven. Cook for 4 - 6 minutes or until the pizza is risen, golden and crisp. Remove from oven and serve immediately. Repeat for remaining pizza.