How to Make It
In a medium bowl, combine half of the thyme with half of the rosemary, the garlic, and crushed red pepper. Add the sirloin and cover with olive oil. Refrigerate for at least 24 hours.
Preheat the oven to 275°. Remove the beef from marinade and season with salt and pepper; discard the marinade. Heat a cast iron skillet. Cook the sirloin over high heat until it is browned on all sides, about 4 minutes. Top the beef with the remaining thyme and rosemary and drizzle with more olive oil and then transfer the skillet to the oven.
Roast the sirloin, basting and turning the beef occasionally, until the sirloin is medium-rare and a thermometer inserted into the thickest part registers 140°, about 20 minutes. Transfer the sirloin to a work surface and let rest until ready to serve.
Using a paring knife, gently score the belly of the shrimp so that it lies flat. This will prevent the shrimp from curling when they cook.
In a large saucepan or straight-sided skillet, combine the rosemary, thyme, garlic, lemon and crushed red pepper. Season the shrimp with salt and arrange them in a single layer in the skillet. Cover the shrimp with olive oil and then poach over moderately low heat until the shrimp is tender and cooked through, about 6 minutes. Transfer the shrimp to a platter.
Slice the sirloin and drizzle with more olive oil and sprinkle with flaky sea salt Transfer to the patter with the shrimp and serve with the roasted vegetables and the salmoriglio.
Make the salmoriglio.