Set a large skillet, a medium bowl, and a plate near the stove so everything is ready when the pan gets hot.

Wrap the tofu in a clean kitchen towel or paper towels and press it gently for 5 minutes to remove extra moisture.

Cut the tofu into 1-inch cubes and keep it on the towel while you prepare the sauce.

Put the harissa paste, tomato paste, lemon juice, 3/4 teaspoon of the salt, and 1/4 cup water into the bowl. Stir until the mixture looks smooth and loose enough to pour.

Place the skillet over medium-high heat and let it heat for about 1 minute.

Add 1 tablespoon of the olive oil to the hot skillet and swirl it across the bottom.

Put the tofu into the skillet in a single layer. Cook for 4 minutes without moving it much, until the bottoms are deep golden brown.

Turn the tofu pieces with tongs or a thin spatula. Cook for 3 to 4 minutes more, until the second side is browned and the edges look firm.

Transfer the browned tofu to the plate.

Add the remaining 2 tablespoons olive oil to the same skillet. Put the red onion into the skillet and cook for 2 minutes, stirring often, until it starts to soften.

Add the chickpeas to the skillet. Cook for 2 minutes, stirring, until they are hot and a few of them start to get light brown spots.

Put the zucchini into the skillet and sprinkle on the remaining 1/4 teaspoon salt. Cook for 4 minutes, stirring every minute or so, until the zucchini is bright and just tender but not falling apart.