Cook the tagliatelle in salted water al dente according to the instructions on the packet, then drain. Drizzle the salmon and prawns with lemon juice and a little pepper. Fry the spring onions in hot oil in a pan, then add the garlic, lemon zest, prawns and salmon and fry for about 6 - 8 minutes while turning. Deglaze with the white wine and add the cream with the granulated broth. Let it reduce a little (about 5 minutes). Season to taste with pepper, salt, sugar, chilli flakes and dill. Arrange the tagliatelle on plates, then pour the salmon, prawns and sauce over them. Decorate with jalapeño slices.