Remove the skin from the shallots or onions and dice very finely. Sauté in 2/3 of the butter until translucent, pour in veal stock and wine and do the whole thing at a high temperature, stirring occasionally, until the onions are quite soft and the liquid has almost completely evaporated. Only now add sherry vinegar and crème fraîche and season the sauce with salt and paprika.
Peel the tomatoes, cut into quarters, remove the seeds completely, remove the green stalks and cut into cubes. Let them “melt” in the remaining butter, i.e. soften only flat, not mousse. season with salt. Rinse basil, dry and mix into tomatoes in strips. Garnish onion sauce with it.
Goes well with: fillet of beef, pork and lamb of all kinds.