In a large cast-iron skillet, heat olive oil over low heat. Cook the onion until soft for about 5 minutes. Then, add the garlic and cook until fragrant for another 3 minutes.
Increase the heat to medium-high, incorporate the chard stems (if sing chard), and cook to release some liquid, about 5 minutes. Add the chard leaves or spinach leaves in batches, adding more as they wilt, and continue cooking, stirring occasionally, until completely wilted, 3 to 5 minutes more. Season with teaspoon sea salt, pour in yogurt and stir together. If the mixture seems too thick, add 1 tablespoon of water at time to your yogurt and greens and stir well. Bring to a simmer.
Create six small indentations in the prepared greens using the back of a spoon. Carefully place one egg into each indentation. Cover with a lid or foil and cook over medium-low heat until the eggs are just set but still tender, approximately 4 minutes for a runny yolk and 5 minutes for a jammy yolk. Uncover, then season with salt, pepper, feta, avocado, jalapeño, and cilantro.
Serve with hot sauce, toasted keto tortillas or green tortilla wraps and lime wedges. Enjoy!
