In a cast iron pan on medium heat, add bacon and cook until fat has been rendered and bacon is crisp. Remove bacon and set aside.
Add garlic, onion and Cubanelle pepper. Sauté until onion is translucent. Sprinkle in the flour and continue to stir until flour is cooked through, an additional 2-3 minutes.
Stream in vegetable stock, constantly stirring until sauce begins to thicken.
Stream in half and half, then add cheeses. Stir until cheese is completely melted and a thick sauce has formed.
Fold in spinach, a cup at a time. Once spinach has wilted completely in cheese mixture, remove from heat and season with red pepper flakes, salt and pepper.
Fold in half of the bacon and sprinkle the remainder on top of dip. Serve with crusty bread.