Heat a lightly greased frying pan on high. Stir-fry beef in batches for 2 minutes, until browned. Remove from pan and keep warm.
Reduce heat to medium and cook onion for 5 minutes, stirring, until soft and golden. Add mushrooms and capsicum and cook for 5 minutes, until just tender. Stir through tomato and paprika and bring to boil. Reduce heat to low and simmer for 5 minutes, until sauce thickens. Stir through beef and season to taste.
Meanwhile, cook gnocchi in a large saucepan of boiling, salted water according to packet directions. Drain. Serve tossed through beef and capsicum.