I have made different versions of this buckwheat egg bake a few times, and have had different results. The biggest problem before was the mixture would come out perfect but the egg would get a little too cooked for my liking.
I've found that the best way to avoid overcooking the egg is to bake everything, and then finish off the eggs under the broiler.
Spinach and Feta Buckwheat Egg Bake
1/2 cup buckwheat groats
2 cups water
Half of an onion, chopped
1 cup spinach
1/2 cup fat-free feta cheese
Salt and ground pepper
1/4 cup walnuts, chopped and toasted
Preheat oven to 350°. Bring water and salt to a boil, add buckwheat groats. Cover and turn to low heat and cook for about 15 minutes, until water is absorbed and the groats are creamy. Drain any extra water and set aside. Cook onions with a pinch of salt and ground pepper until soft, add in spinach and cook until wilted. Remove from heat.
In a large bowl combine the groats, spinach and onion mixture, and half the feta and half the toasted walnuts. Mix to combine, and divide between two oven safe bowls. Top with remaining walnuts and feta. With a spoon, make a well in each bowl and crack one egg into it. Bake for 15 minutes at 350° for the mixture. To finish cooking the eggs, switch the oven to broil and finish baking until the eggs are cooked, about 3 minutes.