- To make the onion rings, in a deep fryer, heat the canola oil to 350°F. Line a baking sheet with paper towels. Season the onion rings lightly with kosher salt.
- Sift the semolina flour, all-purpose flour, sugar, baking soda, baking powder, cornstarch and the 2 teaspoons kosher salt into a large bowl. Add the eggs, vegetable oil and club soda and whisk until just incorporated; do not overmix. Dip about 10 of the onion rings into the batter, then add them to the oil. Fry, shaking the fry basket occasionally, until the onion rings are golden and crispy, about 8 minutes. Transfer to the paper towel lined baking sheet and season lightly with kosher salt. Repeat with the remaining onion rings.
- Preheat an electric indoor grill on high heat according to the manufacturer's instructions. (You may also use an outdoor gas or charcoal grill.) Brush the steaks with the olive oil and season generously with kosher salt and pepper. Arrange the steaks on the grill and cook, turning once, until nicely grill-marked, about 6 minutes per side for medium-rare, or until done to your liking.
- Transfer the steaks to a carving board, cover loosely with aluminum foil and let rest for 5 minutes. Cut the steaks against the grain into slices 1/4 inch thick and sprinkle with sea salt. Pile the onion rings on a platter and arrange the steak slices alongside.
- Serve immediately with creamy truffled spinach.
- CREAMY TRUFFLED SPINACH: In a sauté pan over medium heat, melt 2 tablespoons of the butter. Add half the spinach and cook, stirring often, until wilted, 4 to 5 minutes. Add the remaining spinach and cook until wilted, 4 to 5 minutes. Transfer the spinach to a colander and drain, pressing down on the spinach with a rubber spatula to remove the excess liquid.
- Return the pan to medium heat and melt the remaining 1 tablespoon butter. Add the spinach, then stir in the 1 teaspoon truffle oil, the crème fraîche, salt and pepper. Cook until the spinach is warmed through, 3 to 5 minutes. Stir in up to 1 teaspoon additional truffle oil, if desired.
- Serve immediately.