Bring 3 to 4 liters of water to a boil in a large pot.
Heat the butter and olive oil in a Dutch oven or large skillet over medium heat. Swirl the pan, coating the surface of the skillet.
Once the butter is melted and the oil is shimmering, add the garlic, shallots, fennel, thyme, tarragon, red pepper flakes, and bay leaf. Cook for 8 to 10 minutes until the shallots are translucent and the fennel is tender.
Add the tomato paste and stir to combine. Cook until the tomato paste starts to smell fragrant and begins to brown the bottom of the pan, about 2-3 minutes.
Add the sherry and stir to combine, deglazing the pan by scraping the brown bits (frond) from the pan.
Add the heavy cream and lobster juice and stir to combine. Turn heat up to medium-high and cook for 10-15 minutes, reducing the sauce by half.
While the sauce is simmering, toss the salt into the boiling water. Once the salt is dissolved, add the ravioli and cook according to the package instructions.
While the ravioli cooks, add the lemon juice and zest to the sauce.
Drain the ravioli, reserving the pasta water.
Add a ½ cup to 1 cup of the reserved pasta water to the sauce and stir.
Remove the bay leaf and cook for 2-5 minutes until the sauce has reached your desired consistency. Taste and add salt and pepper to taste.
Add the ravioli and gently stir to coat. Add more reserved pasta water if needed for consistency.
Serve immediately and top with fresh tarragon leaves, a sprinkle of freshly ground black pepper, parmigiano reggiano or pecorino romano shavings, and a spritz of fresh lemon juice.