1: Set up your charcoal grill for caveman grilling (grilling in the embers). Remove the grill grate. Lay the onion, tomatoes, and habanero chiles directly on the coals and cook until charred on all sides, turning with tongs. Transfer to a foil pan and let cool.

2: If using a gas grill, preheat it to screaming hot. Grill the vegetables to char the skins.

3: Scrape off the burnt skins with a paring knife. You don’t need to get off every last bit—a few specks of black will add flavor. For a milder (but still ferocious salsa), seed the chiles. Cut the vegetables into 1-inch pieces. Finely chop or coarsely puree in a food processor. Work in the cilantro, orange and lime juices, and salt, running the machine in short bursts. Correct the seasoning, adding more juice or salt to taste: the salsa should scream with flavor.

4: Place the shrimp in a bowl and season with salt and pepper. Stir in the orange and lime juices and let the shrimp marinate for 20 minutes.

5: Make the cilantro butter: Melt the butter in a saucepan. Add the cilantro and garlic and cook until sizzling, but not brown, 2 to 3 minutes. Remove the pan from the heat and set aside, but keep warm.

6: Place the sour cream, shredded cabbage, avocados, if using, and lime wedges in attractive bowls.

7: If using a charcoal grill, replace the grill grate. If using a grill basket, preheat it on the grill grate and coat it with oil. Otherwise, thread the shrimp on skewers for easier turning, then brush and oil the grill grate.

8: Grill the shrimp until browned and cooked though, 2 minutes per side, basting with the cilantro butter. Tip or unskewer onto a platter. Briefly warm the tortillas on the grill and place in a cloth-lined basket.

9: To serve, have each eater place a few shrimp on a tortilla. Top with cabbage, sour cream, and the chiltomate or other salsa. Serve with lime wedges and grilled avocados, if using.