Slice the tofu into 8 to 10 rectangles, about 1/2-inch thick. Stack the rectangles a few at a time, and then cut each stack so that each rectangular layer becomes 8 square-ish pieces. Repeat until all of the tofu is cut into cubes. If you want to sear the tofu as rectangles, skip the second cutting step, and leave the slabs whole.
Heat a cast iron or other heavy skillet over medium-high heat until it is very hot.
Toss the tofu with 2 teaspoons of vegetable or olive oil (or cooking oil of your choice). When the skillet is hot, add the remaining 2 tablespoons of oil and swirl to coat the bottom of the pan. Add the tofu to the pan in a single layer, watching for splattering. Season lightly with salt. Don’t crowd the pan; if you can’t fit the tofu in your pan in a single layer, do this in two batches (adding a bit more oil to the pan for the second batch).
Cook the tofu until it forms a golden crust on the underside, about 6 to 7 minutes. Using a fork, a spatula, small tongs, or an offset spatula, flip the tofu squares, and brown the other side, about 5 minutes.
Serve immediately, or use in your favorite recipe.