Step 1

Heat your largest well-seasoned cast-iron or nonstick skillet over medium-high heat. (If using cast iron, heat it for 2 to 3 minutes, until very hot, to prevent the tofu from sticking.) Drizzle in 1 tablespoon of the oil and carefully add the tofu slices (the oil may spit, so stand back) in a single layer. Season generously with salt and pepper, and cook, undisturbed, until the bottom is golden, 2 to 3 minutes. Flip the pieces and cook on the other side until the bottom is golden, another 2 to 3 minutes. Transfer to a plate.

Step 2

Return the skillet to the stovetop and reduce the heat to medium. Add the remaining 1 tablespoon of oil, along with the onions, and season with 1/4 teaspoon of the salt. Cook, tossing the onions, until soft and golden, 5 to 6 minutes.

Step 3

Add the harissa and cook, stirring, until the paste starts to caramelize and stick to the pan, about 1 minute. Add the crushed tomatoes and water, and stir to loosen the sauce. Cover and cook until the flavors meld and the sauce thickens, about 10 minutes.

Step 4

Season with the remaining 1/4 teaspoon of salt and a big pinch of black pepper. Taste, and season with more salt and pepper, if desired. Add the tofu to the sauce and let warm through, about 2 minutes.

Step 5

Remove from the heat, top with herbs and serve from the skillet, with crusty bread or flatbread on the side, if desired.