Heat the olive oil over medium-high heat in a large skillet or high-sided pan. Add the onion and cook, stirring occasionally, 4 to 5 minutes, or until softened and translucent.
Add the tomatoes (and cayenne, if using); season with salt and pepper. Cook, stirring occasionally, until the sauce has thickened slightly, about 5 minutes. Fold in the greens.
With a spoon, make four little pockets in the saucy-greensy mess into which you can crack the eggs. Crack them in, season each with a pinch of salt and pepper, and carefully drag the whites through the sauce. Don’t break the yolk. You know this. Mama didn’t raise no fool.
Cover the skillet and cook until the whites are just set, about 4 minutes. Turn off the heat.
Pile a scoop of cooked grains at the bottom of a bowl, then top with a big scoop of saucy-greensy mess and an egg. Sprinkle the crumbled feta over the top, and devour.