At first, Yesenia Castañon, the pastry chef at French restaurant JouJou, just liked the sound of “Sunday Sundae.” Fromage blanc ice cream, olallieberries three ways (fresh, jammed, and preserved), lemon verbena, and brown sugar meringue. With a brand new recipe every week, Castañon tries to find whatever produce is perfectly ripe and in its prime to feature for a sundae. A few Sundays ago, she served a sundae of sungold tomatoes, citrus marigold semifreddo, basil crème diplomat, and vanilla ice cream with a generous pour of strawberry-tomato sauce on top. Her track record of thinking outside the box has emboldened some of her regulars to make requests for similarly uncommon sundae ingredients, such as for the sweet Italian frying peppers known as Jimmy Nardellos.