Preheat the oven to 250 degrees F. Line a baking sheet with foil. Spread 2 tablespoons salt, the coriander seeds, peppercorns, paprika, red pepper flakes, dill seeds and minced garlic in an even layer on the baking sheet and roast until the garlic is dry, about 30 minutes; let cool. Transfer to a spice grinder and pulse several times. (The spiced salt can be made up to 1 week ahead; store in an airtight container.)
Remove the steaks from the refrigerator about 1 hour before grilling to bring to room temperature; sprinkle each side with 1/2 teaspoon of the prepared spiced salt, then cover with plastic wrap and set aside.
Preheat a grill to high and prepare for indirect grilling: On a charcoal grill, bank the coals to one side; on a gas grill, turn off half of the burners. Wipe the salt off the steaks and pat dry; brush lightly with olive oil. Grill over direct heat until marked on the bottom, about 2 minutes, then rotate 90 degrees F and cook 2 more minutes. Flip the steaks and repeat on the other side, then transfer to the cooler side of the grill (indirect heat); cook 5 more minutes per side for medium rare. Transfer to a cutting board and let rest 5 to 10 minutes.
Meanwhile, grill the tomatoes over direct heat, turning, until marked, about 5 minutes. Serve with the steaks and the remaining spiced salt.