Preheat your oven to 425°F and line a baking sheet with parchment paper.
Peel the onion and slice it into 1/4-inch thick rings, separating the individual rings carefully.
In a shallow bowl, whisk together the whole egg and egg white.
In a separate bowl, mix the almond flour with salt, pepper, garlic powder, and dried oregano.
Dip each onion ring first into the egg mixture, ensuring an even coat, then dredge in the almond flour mixture, shaking off any excess.
Place the coated onion rings on the prepared baking sheet in a single layer. For extra crispiness, ensure they are not touching.
Bake in the preheated oven for 15-20 minutes, flipping halfway through, until the coating is golden and crisp.
While the onion rings bake, prepare the dip by combining the Greek yogurt, lemon juice, a pinch of salt, and extra dried oregano if desired. Mix well.
Remove the onion rings from the oven and serve warm with the herbed Greek yogurt dip.