NYT Cooking: Fresh blueberries make these lemon bars a bit sweeter than usual, and very jammy, but without compromising their essential acidity. The grated lime zest gives the curd another note of citrus complexity. But if you’d rather leave out the lime, use more lemon zest. Or try playing with orange and grapefruit zests. The filling stays pretty soft in these tender bars, so it’s best to keep them in the…