How to Make It
In a small bowl, mix the mayonnaise with the capers, chile and 2 tablespoons each of the parsley and chives. Season the herb mayonnaise with salt and pepper.
In another bowl, toss the tomatoes with the olive oil and the remaining 2 tablespoons each of parsley and chives. Season with salt and pepper.
Spread the herb mayonnaise on the rye crisps and top with the tomatoes and sardines. Serve right away.
If available, smoked sardines are delicious here, too.