How to Make It
In a large bowl, whisk the parsley with the cilantro, tarragon, capers, cornichons, garlic, mustards and olive oil.
Cut the cauliflower from top to bottom into four 1/2-inch-thick steaks. Generously season them with salt and pepper. In a very large skillet, heat the canola oil until very hot. Add the cauliflower in a single layer and cook over high heat until browned, 2 to 3 minutes. Carefully turn the steaks, add the wine and cook until it is evaporated and the cauliflower is easily pierced with a knife, 3 to 5 minutes.
Transfer the cauliflower to a platter and sprinkle with the lemon zest. Stir the lemon juice and vinegar into the salsa verde and season with salt and pepper. Spoon the sauce on the cauliflower and serve.