Preheat your oven to 400°F (200°C)

In a large skillet over medium heat, cook the ground beef and chopped onion together until the meat is no longer pink, about 8-10 minutes

Drain any excess fat from the meat mixture if necessary

Transfer the cooked beef and onion mixture to a 9.5-inch pie plate, spreading it evenly across the bottom

Sprinkle the salt evenly over the meat layer

In a medium bowl, whisk together the coconut flour, almond flour, and baking powder

Add the almond milk and eggs to the flour mixture and whisk until smooth and well combined

Pour this batter evenly over the meat in the pie plate, allowing it to soak in slightly

Sprinkle about 1 cup of the shredded cheese over the top

Bake in the preheated oven for 25 minutes, or until the center is set and the top begins to turn golden

If using tomato slices or other toppings, remove the pie from the oven after the initial baking time

Add the tomato slices (if using) and sprinkle the remaining 1/2 cup of cheese on top

Return to the oven for an additional 5 minutes, or until the cheese is melted and bubbly