Heat a deep pot over medium heat. Add the butter, onion, and thyme and sauté until the butter melts and the onion becomes soft and lightly caramelized.
After that add the garlic and cook for another minute until fragrant.
Add the chopped tomatoes and parsley. Deglaze the pot with the white wine and cook for 1–2 minutes until the alcohol evaporates. Season with salt and pepper and stir well.
Add the mussels to the pot, cover, and cook for about 4–5 minutes until the mussels open.
Remove the pot from the heat and gently shake it so the mussels are well coated with the sauce. Adjust seasoning if needed.
Serve the mussels hot with the red sauce, sprinkled with extra parsley.
Enjoy!
Notes
Chef's Tip: Discard any mussels that do not open during cooking, as they are not safe to eat.