Finely grate enough zest from 1 lemon to measure 2 teaspoons. Trim ends of both lemons, then stand lemons on a cut side and cut peel, including all white pith, from lemons with a sharp paring knife (discard peel).
Cut segments free from membranes, then cut segments crosswise into 1/4-inch pieces. Toss lemon segments gently with sugar in a bowl.
Stir in remaining ingredients and zest, then let stand, covered, at room temperature 15 minutes (to allow flavors to develop).
