Caramlized Onion, Bacon and Spinach Pizza

pizza dough homemade or store bought

slices bacon ((7 oz), cooked and chopped)

olive oil (, divided)

baby spinach

large red onion (, sliced 1/4-inch thick slices)

Salt and freshly ground black pepper

granulated sugar

balsamic vinegar

butter

large clove garlic

flour

milk

low-moisture mozzarella cheese (, shredded)

parmesan cheese (, finely shredded)