Soften the onion and garlic in 1 tablespoon of rapeseed oil over a low heat, add the vinegar and sugar, simmer for a few seconds until reduced by half.
Add the passata, peppers and tomatoes and cook on a low heat for 1 minutes.
Season to taste, stir in 1 tablespoon of rapeseed oil, set aside to cool.
To serve
Place 2 slices of smoked salmon or trout in the middle of a plate.
Arrange 3 spears of asparagus around, spoon around 1 tablespoon of the tomato, pepper dressing, top with a tablespoon of crème fraiche.
Garnish with sorrel leaves or herbs of your choice.