The steak is very lightly salted before it's cooked to get flavors going; then once it's cooked and sliced, it's sprinkled with coarse, crunchy sel gris. The finishing salt does all the heavy lifting, flavor-wise, with just a crystal or two popping with every bite. Don't worry if the onion wedges fall apart once you add the peppers to the pan; we keep them as wedges so there are flat surfaces to get a nice bit of char at the beginning.
Serves 4 (serving size: 3 ounces steak and 3/4 cup onion mixture)
1. Heat a large cast-iron skillet over medium-high heat. Sprinkle steaks evenly with paprika, 1/8 teaspoon fleur de sel, and 1/4 teaspoon black pepper. Add 1 1/2 teaspoons oil to pan; swirl to coat. Add steaks to pan; cook 4 minutes on each side or until desired degree of doneness. Remove steaks from pan; let stand 10 minutes.
2. Add remaining 1 tablespoon oil to pan; swirl to coat. Add onion wedges; cook 2 minutes on each side. Add poblanos to pan; sauté 4 minutes, stirring occasionally. Remove from heat; cover and let stand 5 minutes. Stir in remaining 1/4 teaspoon fleur de sel and remaining 1/8 teaspoon black pepper. Arrange onion mixture on a platter. Cut steak across grain into thin slices. Arrange steak over onion mixture; sprinkle evenly with sel gris. Serve with lime wedges.