In a small bowl, dissolve the sugar and yeast in the warm water. Let it sit for about 5-10 minutes until frothy.
In a large mixing bowl, combine the flour and salt. Make a well in the center and add the yeast mixture and olive oil. Mix until a dough forms.
Knead the dough on a lightly floured surface for about 5-7 minutes until smooth and elastic. Place the dough in a greased bowl, cover with a damp cloth, and let it rise in a warm place for about 1 hour, or until doubled in size.
While the dough is rising, prepare the toppings. In a skillet, heat a little olive oil over medium heat. Add the sliced onions and cook until soft and lightly caramelized. Remove from heat and set aside.
Preheat your oven to 400°F (200°C). Once the dough has risen, punch it down and roll it out on a lightly floured surface to fit a baking sheet or pizza pan.
Transfer the rolled-out dough to the baking sheet.
Layer the sliced tomatoes, red and green bell peppers, caramelized onions, black olives, and minced garlic evenly over the dough. Sprinkle with dried oregano, salt, and pepper.
Drizzle a little olive oil over the top of the assembled coca.
Bake in the preheated oven for about 20-25 minutes, or until the edges of the dough are golden brown and the vegetables are tender.
Remove the coca from the oven and let it cool slightly before slicing. Serve warm or at room temperature.
Enjoy your meal!