For the lobster relish: Bring an inch of water to a boil in a large pot with a steamer insert. Set the lobster belly-up on a cutting board. Pierce it with a knife just under the base of the head, and cut it deeply through the belly to kill it quickly. Transfer the lobster to the steamer, cover and cook for 8 minutes.
Meanwhile, add 1 tablespoon of the olive oil along with the garlic to a small saute pan set over medium heat. Cook until golden and fragrant, then transfer the garlic to a medium bowl. Add the tomatoes, red pepper flakes and lemon zest and juice to the bowl. Sprinkle with salt and pepper and set aside.
The moment the lobster is done shock it in an ice bath to stop cooking. When cool enough to handle, pull off the tail and claws and remove the meat. Chop up the meat and add it to the tomato mixture. Drizzle with some olive oil.
In another saute pan, heat the remaining 1 tablespoon olive oil over medium-high heat. Add the lobster-tomato mixture and heat it through. Add the white wine and cook for another minute. Remove from heat and stir in the parsley and oregano.
For the steak: About 20 minutes before cooking, remove the steak from the refrigerator and let it sit, covered, to come up to room temperature. Mix together the ancho powder, paprika, mustard, salt, cayenne, coriander, cumin and black pepper in a bowl and set aside.
Preheat a large cast-iron pan over high heat and set the oven to broil.
Brush the steak on both sides with the canola oil and season liberally with salt and pepper. Sprinkle one side of the steak with the spice rub. Drizzle a little canola oil in the pan; when it begins to smoke, add the steak rub-side down and cook until a nice crust forms, about 2 minutes.
Transfer the steak to a cutting board and slice it against the grain 1-inch thick. Return the steak to the pan, rub-side up. Scatter the butter on top and broil to medium-rare, about 4 minutes. Remove the pan from the oven and baste the steak with the pan juices.
Assembly: Arrange the steak and the lobster relish on a plate. Drizzle with 1 tablespoon of the steak juices. Garnish with oregano and parsley.