In a medium-to-large skillet (at least 10 inches) over medium heat, heat the oil until shimmering. Add the onions and cook, stirring occasionally, until soft and translucent, about 6 minutes. Add the bell pepper and jalapeño and cook, stirring occasionally, until just softened, 3 to 4 minutes. Stir in the tomato paste, 1 tablespoon of the harissa and the garlic, and cook, stirring constantly, for an additional 2 minutes.

Stir in the crushed tomatoes, salt, sugar, paprika, cumin and caraway. Bring the mixture to a boil, reduce the heat to low and simmer uncovered until the sauce is thick, shiny and somewhat reduced, about 20 minutes. Taste, and adjust the seasoning, adding more salt or the remaining harissa, if you like it spicier.

While the sauce cooks, position a rack in the middle of the oven and preheat to 400 degrees.

Remove the skillet from the heat. Using a large spoon, create 6 to 8 little wells in the sauce, depending on how many eggs you are using. Carefully break 1 egg into a cup or ramekin, then slip it into one of the wells; repeat with the remaining eggs. (Cracking the egg into a cup first lets you inspect it for any runaway bits of shell.) Transfer the skillet to the oven and bake until the egg whites are set but the yolks are still a little runny, about 12 minutes.

Transfer the skillet to the counter and sprinkle with the herbs and feta, if using. Drizzle with more olive oil, to taste. Serve the shakshuka directly from the skillet, with plenty of bread.