Preheat oven to 375°F. Spray a 9-inch pie plate with baking spray and dust it with a little of the almond flour.
Heat a large non-stick pan over medium heat. Add 2 teaspoons olive oil, and then the grated sweet potato, garlic powder, 1 teaspoon salt, and 1/2 teaspoon pepper. Cook while stirring occasionally for 5 minutes until potatoes are soft and start to sizzle.
Transfer this sweet potato mixture to a mixing bowl to cool slightly.
Add 1 egg to the cooled sweet potato mixture along with the remaining almond flour. Mix completely.
Press into the prepared pie plate and bake for 15 minutes, until the crust is slightly golden and set. Remove from oven and set aside.
Quiche Filling & Assembly
Heat a large non-stick pan over medium heat. Add 2 teaspoons olive oil, and then the onion, bell pepper, garlic, oregano, 1 teaspoon salt, and 1/2 teaspoon pepper. Cook for 2 to 3 minutes until onion and bell pepper start to get soft, stirring occasionally.
Add the spinach and cook until wilted. Remove from the heat.
In a large mixing bowl, beat the 6 eggs with the milk and whipping cream.
Stir in the cooked onion, bell pepper, spinach mixture. Stir in 1.25 cups of the grated cheddar. Pour this mixture into the reserved pie plate with baked sweet potato crust.
Top with the remaining 1/4 grated cheddar and bake for 30 to 35 minutes, or until the edges are golden brown and the center is set (cover the pie crust edge with foil if the crust is getting too dark).
Let rest for 10 minutes before cutting into 6 or 8 pieces.