- Prepare a charcoal grill for two-zone cooking and build a medium fire, or heat a gas grill to medium-high. Carefully wipe preheated grates with a lightly oiled paper towel. Using a grill brush, scrape grill grates clean, then carefully wipe with lightly oiled towel again.
- Halve fennel bulb lengthwise and cut each half into 1-inch wedges, keeping the root intact to help the wedges hold together on the grill. Cut onion into ½-inch rounds. Quarter radicchio, keeping the stem intact.
- Grill fennel, onion, and radicchio over direct heat, turning as needed for even cooking, until the fennel and onion are lightly charred and cooked through but still have a little bite, about 20 minutes. The radicchio is ready when the leaves are wilted and the tips crackly, about 15 to 20 minutes.
- As they finish, place grilled vegetables in a bowl and cover with plastic wrap. Once fully cool, chop vegetables into roughly ½-inch pieces. Return vegetables to bowl and combine with oil, vinegar, salt, garlic, capers, and chiles. Stir in mint and marjoram.
- On a baking sheet or large plate, brush or drizzle each steak with 2 teaspoons olive oil and season generously with kosher salt on both sides. Carefully place fish on grill over direct heat. Cook 3 to 4 minutes per side for medium rare, 120 to 125 degrees.
- Transfer fish to a serving dish. Top with vinaigrette, lightly drizzle with olive oil, sprinkle with pepper and flaky salt, and serve with lemon wedges.
8 or 9 tomatillos, husked and rinsed
1 onion, quartered through the root
2 or 3 serrano or jalapeño chiles (as desired for heat)
2 or 3 garlic cloves, unpeeled
1 cup fresh cilantro (leaves and tender stems)
1 to 2 tablespoons fresh lime juice
- Prepare a charcoal grill for two-zone cooking and build a medium fire, or heat a gas grill to medium-high. Carefully wipe preheated grill grates with a lightly oiled paper towel. Using a grill brush, scrape the grates clean, then carefully wipe with lightly oiled towel again. If using a grill basket, allow it to heat for 10 minutes before cooking.
- Working in batches if necessary, grill tomatillos, onion, chiles, and garlic over direct heat until the vegetables are blackened and blistered on all sides, 4 to 6 minutes for the tomatillos and chiles, a few minutes longer for onion and garlic. Transfer to a baking sheet to cool.
- Stem the chiles, peel the garlic, and put them in a food processor. Add the tomatillos, onion, cilantro, and lime juice and process until mostly smooth. Season to taste with salt.