Preheat your oven to 375°F (190°C). Lightly grease a 9x9-inch baking dish or similar casserole dish.
Cook the bacon in a large skillet over medium heat until crisp, about 6–8 minutes.
Transfer to a paper towel–lined plate. Reserve 1 tablespoon of bacon fat in the skillet.
Add the onion to the skillet and cook 2–3 minutes until softened. Stir in the garlic and cook 30 seconds, just until fragrant.
Add the spinach, a handful at a time, and sauté until wilted and most of the moisture cooks off, 2–3 minutes.
Remove from heat and let it cool slightly.
In a large bowl, whisk the eggs, heavy cream, salt, pepper, and smoked paprika. Stir in the cheese, most of the cooked bacon, and the spinach mixture. Taste and adjust seasoning if needed.
Pour the mixture into the prepared baking dish.
Sprinkle the remaining bacon on top for a crisp finish.
Bake for 22–28 minutes, or until the center is just set and the edges are lightly golden. The center should no longer jiggle.
Let it rest 5–10 minutes before slicing. This helps it set and makes cleaner cuts.