Pierce each tomato once with a small sharp knife – this helps to release the juice while the tomatoes are cooking. Place them in a roasting tin in which they fit quite snugly. Drizzle over a little olive oil and season with salt and pepper. Roast on the middle shelf of the oven for 20 minutes or until the tomatoes are soft and bursting from their skins. Set aside to cool.
Pound the rosemary leaves, garlic and anchovy fillets to a rough paste, using a pestle and mortar. Add the tomatoes one by one, pounding after each addition, until all have been incorporated. Add the mustard and wine vinegar and stir well to combine. Pour in the olive oil, stirring as you do so. Taste and season with a little salt and pepper. The dressing should be quite coarse and textural. Set aside to allow the flavours to adjust to each other.
To cook the asparagus, place a large pan of well-salted water on to boil. Snap the asparagus spears near the base – they will naturally break off where the fibrous part ends. Peel the lower end of the stalks. When the water is boiling vigorously, drop in the asparagus and cook for 1 ½ minutes or until the spears are still firm but yield to the bite. Remove with tongs and place in a warm bowl.
Immediately season the asparagus and dress with extra virgin olive oil. Arrange on warm plates, add a dollop of crème fraiche and spoon on the tomato dressing. Finish with rosemary flowers, if available, or sprinkle with a little chopped parsley and serve.