Preheat the oven to 350°F. Line 8 muffin cups with liners and spray the liners with nonstick spray.
In a large bowl, whisk together the eggs, salt, garlic powder, and cayenne.
Using a rubber spatula, mix in the almond flour, baking soda, cheddar, and parmesan. The batter will be thick and dough-like. You can actually work it with your hands, as shown in the video, although it's quite sticky.
Using a 4-tablespoon scoop, divide the batter evenly between the muffin cups.
Bake until the muffins are golden and a toothpick inserted in their center comes out clean, 22-25 minutes.
Cool the muffins for 5 minutes in the pan, then transfer them to a cooling rack to cool for 5 more minutes before serving.
Video
Notes
Occasionally, baking soda can cause a reaction in baked goods that results in an ammonia smell. If you're concerned about it happening, use 2 teaspoons of baking powder (gluten-free if needed) instead of baking soda. Make sure the baking powder is fresh and not expired.
Please use blanched, finely ground almond flour and not coarse almond meal. It's possible that almond meal would work, but the texture could be dense and not as fluffy, and you also risk the muffins coming out too dry.
The batter should be thick - thick enough to knead. However, if it seems very dry, add 1-2 tablespoons of water.
To minimize sticking, use greased foil or parchment liners or silicone muffin cups. The muffins tend to stick to standard paper liners.
You can keep the leftovers in an airtight container in the fridge for 4-5 days. Reheat them in the microwave at 50% power, starting with 10 seconds per side.
You can also freeze these muffins in freezer bags for up to 3 months. It's easy to defrost them in the microwave.