Boil the lobster tails in salted water for 8-10 minutes until cooked.
Remove the lobster meat and chop it into small pieces; set aside.
In a large pot, sauté the diced onion and minced garlic in butter until translucent.
Add the tomato paste and cook for another 2 minutes to enhance flavor.
Pour in the sherry and let it simmer for 3-4 minutes to reduce.
Add the seafood stock and thyme; bring to a boil.
Reduce heat and let it simmer for 15 minutes for flavors to meld.
Use an immersion blender to puree the soup until smooth.
Stir in the heavy cream and return to low heat.
Mix in the chopped lobster meat and season with salt and pepper to taste.