Bring a large pot of heavily salted water to a boil. Cook the pasta 1 -2 minutes less than the package directions. Save about 1 cup of the pasta water and drain the pasta.

Place the pine nuts, lemon juice, garlic, sea moss powder, ½ teaspoon salt, and pepper in a food processor and pulse several times until finely chopped. Add the basil and pulse until combined. With the machine running, slowly add about ⅓ cup of olive oil. Process until smooth, adding more olive oil if needed.

In a large skillet, add the pesto, about ½ cup pasta water, brie, and tomatoes and cook slowly over medium heat until the brie melts. Add the cooked pasta, spinach, shrimp, and red pepper flakes if using. Cook, stirring gently until the spinach is wilted and the shrimp are cooked, about 3 minutes. Add more pasta water if needed. Garnish with extra basil and a drizzle of olive oil.