Cook spaghetti in a large pan of salted boiling water until not quite al dente
Finely dice shallot
In a large frying pan, melt butter in the oil
Add chilli flakes and shallot to pan and fry until shallot is softened
Add tomatoes and cook until they are soft and juicy (5-8 minutes)
Add lobster / prawns and warm through
Drain pasta reserving a cup of the cooking liquid
Add pasta to frying pan
Stir and cook until pasta is fully cooked, adding pasta cooking liquid as required
Serve topped with lemon zest, with lemon wedges on the side to squeeze over