How to Make It
Combine all of the ingredients in a small bowl.
Season the tuna steaks all over with salt, pepper and the herbes de Provence. In a large nonstick skillet, heat the canola oil until shimmering. Add the tuna and sear over high heat until golden, about 30 seconds per side. Transfer the tuna steaks to a cutting board and slice them 1/4 inch thick.
Arrange the fennel on plates, top with the tuna and drizzle with the sauce vierge. Squeeze the lemon over the tuna and serve.