Prepare the pizza dough: In a large bowl, dissolve the yeast and sugar in the warm water. Let it sit for about 5 minutes until frothy.

Add the olive oil, salt and 2 cups of flour to the yeast mixture. Mix until combined.

Gradually add the remaining flour, 1/2 cup at a time, until a soft dough forms.

Turn the dough out onto a floured surface and knead for about 6-8 minutes, until the dough is smooth and elastic.

Place the dough in a lightly oiled bowl, cover with a damp cloth, and let it rise in a warm place for about 1 hour, or until it has doubled in size.

Punch down the dough and divide it into two equal portions. Roll each portion into a ball and let them rest for 10 minutes before rolling out.

Heat oven to 475 F. If using a pizza stone, place it in the oven to heat up

On a lightly floured surface, roll out each portion of the dough into a 12-inch circle. Transfer each dough to a pizza peel or a baking sheet lined with parchment paper.

Spread a thin layer of pizza sauce over each dough, leaving a small border around the edges. Sprinkle half of the shredded mozzarella cheese evenly over the sauce on each pizza.

Arrange the sliced salami, fresh spinach leaves and red onion slices over the cheese. Feel free to add more or less of any ingredient based on your preferences.

Sprinkle the grated Parmesan cheese, dried oregano and crushed red pepper flakes (if using) over the top.

Transfer the pizzas to the heated pizza stone or place baking sheet in the oven.

Bake for 10-12 minutes, or until the crust is golden and the cheese is bubbly and slightly browned.

Remove the pizzas from the oven and let it cool for a few minutes before slicing and serving.