In a large skillet, warm olive oil over medium heat. Add bacon to skillet and cook for 4 to 6 minutes, until crispy. Transfer to a paper towel-lined plate and pour off and reserve all but about 2 tablespoons bacon fat. Crumble the bacon and set aside.
Add onion and cauliflower florets to the skillet. Mix well, cover and cook for 10 minutes over medium-low heat. Uncover and cook for 8 to 10 minutes, until fork tender. Deglaze with the juice of lemon. Add the cooked pasta and reserved 1/2 cup pasta cooking water. Mix in 1/2 cup Parmesan.
In a small skillet, add the breadcrumbs, reserved bacon fat, lemon zest and pinch of pepper flakes and cook over medium heat, until crisp, 2 to 4 minutes.
Serve pasta topped with breadcrumbs, crumbled bacon, chopped parsley and more Parmesan.
In a large skillet, combine 2 thinly sliced onions, 3 tablespoons olive oil and large pinch of salt.
Cook over medium-low heat for 45 to 55 minutes, stirring occasionally, until onions are soft and golden brown. Store in an airtight container in the refrigerator for up to a week. Makes about 2 cups.