Place two of the tortillas on work surface. Spread each with half of the refried beans and sprinkle evenly with half of the cheese, leaving about a ¼-inch border around the edge to account for melting.
In a 12-inch skillet (nonstick or cast iron), warm the olive oil over medium heat. Add garlic and cook, stirring, for 30 seconds. If there is liquid in the pan, drain it before proceeding. Divide spinach between tortillas and arrange over cheese.
Place one of the remaining tortillas on top of each quesadilla.
Wipe out the skillet and set over medium heat, then cook quesadillas one at a time until lightly browned and crisp on the outside and melty on the inside, flipping once, a few minutes per side. (Or see below for oven instructions.)
Cut into wedges, top with pickled onions, cilantro sauce, sliced avocado and sour cream if you want to go nuts like I always do. Otherwise, they're great with sour cream and your favorite jarred salsa.
Notes
Flour tortillas make great quesadillas, but you can use corn or other gluten-free ones if you prefer. If you prefer, use 6- or 8-inch tortillas for individual dinners.
Here's how to make your own refried beans. To make this recipe vegetarian, use vegetarian beans.
Mexican-style shredded cheese blend makes things easy and tasty, but you can use jack or pepper jack, cheddar, or any other cheese that melts well and has an amenable flavor profile.
To cook quesadillas in the oven, preheat oven and two sheet pans to 400°F. Spray hot pans with cooking spray. Place one quesadilla on each sheet pan and bake for 5 minutes, then flip and bake about 5 minutes more. I(f you're the type of cook who likes top-secret pro-tip life hacks, you can bake your quesadillas between two sheet pans to crisp both sides at the same time and not have to flip them.)
Quesadillas will be at their best shortly after cooking, but you've got options. You can prep and assemble them in advance and store, tightly wrapped, in the fridge for up to a couple of days or in the freezer for a few months, then cook and top right before serving. (To freeze, wrap well and place on cookie sheets until frozen solid to preserve their shape.) Or you can cook them up to a few hours in advance and reheat in a 300°F oven right before serving.
Leftovers (especially if not topped) will keep for a few days in the fridge. You can reheat them in a toaster oven or 300°F oven before serving.
I first published this recipe here in 2018. I've updated the post for clarity, but the recipe remains the same.