How to Make It
In a mini food processor, combine the anchovies and red chile and puree until smooth. Spread the mixture all over the steaks and season lightly with salt and pepper. Refrigerate for 1 hour. Bring the steaks to room temperature before grilling.
Light a grill and oil the grate. Brush the onion with oil and season with salt and pepper. Grill over moderately high heat, turning once, until softened and lightly charred, about 8 minutes. Transfer to a work surface. Grill the tomatoes cut side down over moderately high heat until lightly charred, 3 to 5 minutes. Transfer to a work surface and let cool slightly. Cut the onion and tomatoes into 1/2-inch pieces and transfer to a medium bowl. Stir in the vinegar, chives and the 1 1/2 tablespoons of olive oil. Season the relish with salt and pepper.
Grill the steaks over moderately high heat, turning once, until lightly charred on the outside and medium-rare within, 6 to
8 minutes total. Transfer to plates and let rest for 5 minutes. Serve with the relish.