Place the pasta in a saucepan of boiling water with some coarse salt. Let cook for around 7 min. Drain and let cool.
Rinse the tomatoes and chives.
Peel the red onion. Cut it in half, then slice finely.
Slice the cherry tomatoes in half and finely chop the chives.
Mix the oil, vinegar and mustard together in a bowl. Season with salt and pepper.
Open the can of sardines.
Mix the vinaigrette into the pasta with the cherry tomatoes, chives, red onion and sardines.
As a variation, replace the chives with basil or tarragon and the olive oil with hazelnut or walnut oil.