Heat the oven to 180°C fan. Lightly oil a 6-cup muffin tin, or line with paper cases and grease them well.
Warm the olive oil in a small frying pan over medium heat. Add the onion with a small pinch of salt and cook for 5–6 minutes until soft and translucent. Add the garlic and cook for 30–45 seconds until fragrant, then remove from the heat and allow to cool slightly.
In a large bowl, whisk the eggs until just combined. Add the cottage cheese and whisk briefly to loosen — the mixture should be fluid but still lightly textured.
Stir in the cooled onion mixture, lemon zest, dill, coconut flour, salt, and black pepper. Mix thoroughly, then let the batter rest for 3–5 minutes so the coconut flour can hydrate and thicken.
Fold in the feta (and olives, if using). Divide the mixture evenly between the muffin cups, filling them almost to the top. If using Parmesan, grate a small amount over the surface.
Bake for 25-30 minutes, until set in the centre and lightly coloured at the edges. A knife inserted should come out clean, with no wet egg mixture.
Leave the muffins in the tin for 10 minutes, then transfer to a rack to cool.