In a spice grinder, combine the bay, 2 teaspoons salt and 1 teaspoon pepper, then pulverize to a fine powder. Transfer to a small bowl. In a medium bowl, combine 2 teaspoons of the bay salt, 1 tablespoon of garlic and 1 tablespoon oil, then mash with a fork until combined.

Add the beef and toss, rubbing the seasonings into the meat. Thread the beef onto four 10- to 12-inch metal skewers alternating with the tomatoes; set aside.

In a small saucepan over medium, heat the remaining 2 teaspoons oil and the remaining bay salt, stirring, until fragrant and sizzling, about 3 minutes. Add the remaining 1½ teaspoons garlic and cook, stirring, until fragrant and sizzling, about 10 seconds.

Add the Madeira and bring to a simmer, then reduce to low and cook, stirring, until reduced to 2 tablespoons. Cover and set aside off heat.

Prepare a charcoal or gas grill. For a charcoal grill, ignite a large chimney of coals, let burn until lightly ashed over, then distribute evenly over one side of the grill bed; open the bottom grill vents.

Heat the grill, covered, for 5 to 10 minutes, then clean and oil the grate. For a gas grill, turn all burners to high and heat, covered, for 15 minutes, then clean and oil the grate.

Place the skewers on the hot side of the grill (if using charcoal). Cook, uncovered, until the beef is lightly charred on both sides and the center of the thickest piece reaches 125°F for medium-rare, 10 to 14 minutes total, flipping once about halfway through.

Transfer to a platter, tent with foil and let rest while you make the sauce.

Set the pan with the Madeira reduction over medium and heat uncovered just until steaming. Remove from the heat, add the butter and swirl the pan until the butter is melted and the sauce is emulsified. Remove the meat from the skewers and drizzle with the sauce.