Ingredients

1. 4 pounds tuna steaks, cut 1-inch thick
2. Pure olive oil for brushing, plus more for frying
3. Salt and freshly ground pepper
4. 1 cup finely chopped cornichons
5. 1/2 cup finely chopped red onion
6. 1/4 cup finely chopped dill
7. 2 tablespoons capers, drained
8. 2 tablespoons finely chopped black olives
9. 2 cups mayonnaise
10. 3 tablespoons fresh lemon juice
11. 1/4 cup Dijon mustard
12. 2 tablespoons dry mustard
13. All-purpose flour, for dusting
14. Marinated Cabbage Slaw 

Directions

1. Preheat the broiler. Brush the tuna steaks on both sides with olive oil and season with salt and pepper. Broil half the tuna steaks for 2 minutes per side, until just rare. Repeat with the remaining tuna steaks. Let the tuna cool to room temperature, then finely chop it with a knife.
2. In a large bowl, combine the tuna with the cornichons, red onion, dill, capers and olives. Fold in 1 cup of the mayonnaise and the lemon juice and season with salt and pepper. Form the tuna into 10 burgers and transfer to a baking sheet. Refrigerate until firm, about 30 minutes.
3. In a small bowl, whisk the remaining 1 cup of mayonnaise with the Dijon and dry mustards. Season with salt and pepper. Refrigerate the mustard mayonnaise until it is ready to use.
4. Dust the tuna burgers with flour. Heat 1/4 inch of olive oil in each of 2 large skillets until shimmering. Add 3 or 4 burgers to each skillet and cook over moderately high heat until browned and crisp, about 3 minutes per side for medium. Drain the tuna burgers on paper towels and cook the remaining burgers in 1 skillet. Serve the tuna burgers with the mustard mayonnaise. Pass the Marinated Cabbage Slaw separately.

Make Ahead

The recipe can be prepared through Step 3 and refrigerated overnight.