In a perfect world, Concord grapes would be seedless, and I could bake with them. They’re not, so I had accepted the fact that a great grape tart would never be. Then one day, Eileen Farnan of Buzzard Crest Vineyards brought the most delicious organic seedless grapes to the Greenmarket. Not Concords, but Himrods, Canadice, and Niagaras—varietal grapes grown in the Finger Lakes region of New York State. They come from a harvest so small that we get only enough to make these tarts for a week or two each year. You don’t need to use special varietal grapes at home, but try to find organic grapes from small growers.