In a small soup pot, heat the butter and sauté the veggies, herbs, and salt over medium heat until onions are soft, not brown.
Add the tomato paste and cook briefly.
Add the sherry and bring up to a boil.
Lower heat and add the lobster stock. Cover and let simmer for 10 minutes.
Strain into a clean pot, discarding solids.
Bring liquid back to a simmer and add the rice. Cover and cook for 20 minutes.
Purée in a blender, or use a stick food processor, and process till smooth. Strain again if desired.
Place back on heat and add the cream and lobster.
Taste and season with the cayenne pepper, an additional splash of sherry, and salt if needed. Serve with any additional lobster meat.