Pour water ⅓ of the way up a 9×13 pyrex dish or larger roasting pan (it will need to hold the muffin tray). Set aside. Grease a 12-cup muffin tin. Using a silicone muffin tray works best if you have one.
Beat the eggs, salt and pepper in a pourable bowl.
16 egg, ½ tsp salt, 1/8 tsp pepper
Divide cheese, spinach and red peppers between the 12 muffin cups, then evenly fill with the beaten eggs.
½ cup feta cheese, 1 cup spinach, 1 cup red bell pepper
Cover the muffin tray with a sheet of parchment paper, then tightly cover with foil. Place the water filled roasting pan in the oven, and then place the muffin tray in the water filled roasting pan. Leave uncovered.
Bake for 75-80 minutes.
Remove the water bath with the muffin tray in the water bath from the oven and let them rest in the water bath until the water is cool. Remove the tray, the parchment and the foil, and then remove the omelettes from the muffin cups.