Put a large nonstick or well-seasoned skillet on the stove over medium heat. Set a medium bowl and a plate nearby so the shaping and cooking steps are easy to manage.

Open the tuna cans and drain the tuna very well. If it looks wet, press it lightly in a colander with the back of a spoon so the cakes will hold together.

Crack the egg into the medium bowl and beat it with a fork until the yolk and white are fully mixed.

Add the drained tuna to the bowl. Break it into small flakes with the fork.

Add the cornmeal, about two thirds of the sliced scallions, about half of the chopped parsley, all of the lemon zest, 1/2 teaspoon of the salt, and 1/4 teaspoon of the black pepper to the bowl.

Stir the tuna mixture until it looks evenly combined. Let it stand for 5 minutes so the cornmeal can absorb moisture and firm up the mixture.

Divide the mixture into 6 equal portions and shape them into small cakes about 1/2 inch thick. Press each one firmly so the edges do not crumble, then set them on the plate.

Add 2 tablespoons of the olive oil to the hot skillet and swirl to coat the bottom.

Put the tuna cakes into the skillet in one layer. Cook them for 3 to 4 minutes, until the bottoms are deep golden brown and release easily from the pan.

Flip the cakes with a thin spatula. Cook for 3 to 4 minutes more, until the second side is golden brown and the cakes feel set in the center.

Transfer the tuna cakes to a clean plate. Lower the heat under the skillet to medium-low.

Add the remaining 1 tablespoon olive oil and the minced garlic to the same skillet. Cook for about 30 seconds, stirring, until the garlic smells fragrant but has not browned.