Activate the yeast by mixing the sugar, yeast, and warm water in a bowl. Let it sit for 5-10 minutes to make sure it’s active (it must form bubbles). Then add it to the flour, salt, and olive oil and mix together to form the dough.
On a well-floured surface, transfer your dough and start kneading it till it’s soft and of a smooth consistency. It should take about 5 minutes of kneading.
Transfer the dough to a bowl greased with oil. Cover the bowl with plastic wrap and let the dough rest in a warm place for at least 30 minutes or until the size is doubled.
When the dough is doubled in size, start spreading it on a floured surface into a 12-inch circle. Put the dough on the pizza stone or the baking tray and poke a few holes with a fork.
Slice your red onions into thin slices. Cut the mozzarella cheese into cubes.
Start spreading your tomato sauce on the pizza after brushing a thin layer of olive oil on the surface. Spread the mozzarella cubes generously, and on top, add the fine slices of onions and sardines on top.
Bake the pizza in a preheated oven at 450°F for 15 minutes until edges are crusty enough and the cheese melts.
On a wooden cutting board, transfer your pizza, sprinkle on top the chopped parsley or basil. Slice and enjoy!