For the peanut sauce, peel the peanuts, roast them in a dry pan until brown all over and let them cool down. Blend the peanuts with the coconut milk and the piece of chili pepper in a stand mixer until coarse or very fine, depending on your taste.
Pour sauce into a saucepan, add soy sauce and grated lemon zest and simmer for 2-3 minutes. If you want the sauce thinner, add a little water.
Season sauce with soy sauce and lemon juice.