Wrap the tofu with a kitchen towel to remove moisture.
Blend tofu, doenjang (soybean paste), chili powder, erythritol, minced garlic, vinegar, and sesame oil in a blender until smooth.
Sauté chopped onions in a pan, then add the blended sauce and simmer over medium heat for 5 minutes.
Season with salt and pepper.
Cool the finished sauce and store in a container.