In a large pot or saucepan, heat the soy milk over medium-low heat until it reaches a temperature between 170°F and 180°F. Use a thermometer to monitor the temperature.

Once the milk reaches this temperature, remove it from heat and stir in 2 tablespoons of lemon juice or apple cider vinegar. Let the mixture sit for 5-10 minutes until it curdles and separates into solid curds and liquid whey.

Line a colander with two layers of cheesecloth or muslin cloth and place it over a large bowl.

Carefully pour the curdled soy milk into the lined colander, allowing the liquid whey to drain through. Gently press down on the curds to release more liquid.

Gather up the edges of the cheesecloth and twist to form a ball with the curds inside. Squeeze out any remaining liquid.

Place the wrapped tofu ball on a flat surface and place a heavy object (like a cast iron skillet or book) on top to press down and remove more liquid. Leave for 20-30 minutes.

Unwrap the pressed tofu and shape it into desired form (blocks, cubes, etc.). If you have a tofu press, use it to press the tofu for an additional 20-30 minutes.

Store the homemade tofu in an airtight container with cold water and refrigerate until ready to use. Use within 3-4 days.