Bourgogne des Flandres, at the corner of Dijver canal near the Groeningemuseum, is a reliable spot for traditional Belgian cooking in a setting that doesn't feel like a tourist trap. The kitchen is straightforward — waterzooi (the Ghent chicken or fish stew that also appears in Bruges), rabbit in Belgian beer sauce, stoofvlees (beef braised in Trappist ale) — and does these dishes well. The terrace overlooks the canal and is one of the better spots in Bruges for an unhurried lunch in good weather.
Prices are not cheap — this is the tourist centre of Bruges — but they are honest for what you get. The house beer, brewed in collaboration with the Halve Maan brewery, is a pleasant blonde worth trying. Reservations are advisable for dinner.