In a pot, over medium heat, heat 2 tsp. of oil.
Add the seitan sausage and cook until it's browning; about 3 minutes.
Remove from the pan and set aside.
Add the remaining 2 tsp. of oil, onion and a pinch of salt.
Sauté for 8 to 10 minutes until the onions are soft and lightly caramelized.
As the onions cook, anything stuck to the bottom of the pan from cooking the sausage will lift up.
Add the garlic, salt, herbs and a pinch of red pepper flakes; cook for 1 minute.
Add the tomatoes and sausage; cover the pot and bring the sauce to a simmer.
Turn the heat to low and cook for about 15 minutes.