In a large pot over medium heat, melt the unsalted butter. Add the diced onion and minced garlic, sautéing until the onion is translucent and fragrant, about 5 minutes.

Stir in the tomato paste and cook for an additional 2 minutes to deepen the flavors.

Gradually pour in the seafood stock while stirring to combine. Bring to a gentle simmer and allow to bubble softly for 10 minutes.

Gently fold in the lump crab meat, shrimp, and lobster tail. Reduce heat and simmer until the shrimp turns pink and opaque, about 5 minutes.

Using an immersion blender, purée half of the bisque until smooth while leaving some chunks for texture.

Taste and adjust the seasoning with salt and pepper before serving hot, garnished with fresh herbs if desired.