Long before the June solstice, summer is heralded by Memorial Day, picnics, backyard barbecues, and abundant yellow crookneck squash. This colorful squash dish with red bell pepper and fresh basil or dill (suit yourself) is great for summer entertaining, and it travels well to a potluck. I tasted something like this dish once at a potluck supper way back, and of course, since I live in the South, it would have been smothered with cheese. I think this dish proves the winning possibility of creating a casserole without cheese that everyone will still love —