In a hot sauté pan, saute the diced mushrooms & onion in enough oil to cover the bottom of the pan. Season with salt & pepper. Once they are tender & lightly browned, stir in the minced garlic. Cook for another 1-2 minutes, stirring often.
Brush tortilla with oil and place on a griddle or large pan. Cook on both sides until lightly browned. Remove to a baking sheet. Repeat with the other tortillas.
Spread spinach and artichoke dip evenly on top of each tortilla to within 1/2 inch of the edge. Top with the cooked mushroom & onion mix, then the diced tomatoes. Evenly sprinkle the pizzas with the mozzarella cheese. Cook at 350 until the cheese is melted. Sprinkle with the shredded Parmesan cheese & slice into wedges to serve.
Note: the spinach artichoke dip makes about double of what you need. Place the rest in a small casserole dish & bake at 350 for about 30 minutes to serve as a dip. You can also keep it in the fridge for future pizzas... or increase the pizza servings to use it all up. Using premade spinach artichoke dip is also an option.