A dry white wine is ideal with these buttery tarts. Look for one with enough acidity to underline the contrasting notes from the olives and onions. Crisp Sauvignon Blanc is an obvious choice, but a deep-flavored Chardonnay-based wine, such as the 1996 Château de Maligny Chablis Premier Cru Fourchaume from France or the 1995 Byron Santa Barbara, would be more interesting.