Place the tomato in a blender and purée, then strain through a fine-mesh sieve; you should get about ½ cup (120 ml). Add the butter to a large skillet and gently cook over medium heat until it starts to brown and smell nutty. Stir in the smooth tomato purée (be careful; it might spatter) and simmer for another minute or so. You’re looking to slightly cook the purée but keep its brightness. The mix won’t emulsify, which is fine. Season with salt and pepper and set aside.