By Leslie Brenner

Looking for 78.5 square inches or 2,026 square centimeters of Pi Day deliciousness? Consider this pissaladière — an onion and anchovy tart that’s traditional in Provence, France.

Its base is a surprisingly easy pâte brisée (savory pastry) that comes together in a flash in the food processor. No need to blind-bake it. Fill it with slowly caramelized sliced onions, then top with a lattice of anchovy fillets dotted with pitted niçoise (or kalamata) olives and sprinkle with fresh thyme. Pop it in the oven and bake till golden brown. Those anchovies melt dreamily into the onions, which have already cooked down to rich sweetness.

A nice slice makes a wonderful light dinner, or a superb first course when friends come for dinner. Or take the whole tart — room temp — on a picnic.

At their home in Provence, pissaladières are sometimes built on bread rather than pastry crust, but I favor the pâte brisée tart-crust version, which is what qualifies it as a Pi Day treat. I learned it from a remarkable French cook (and old friend), Danièle Mazet-Delpeuch.

It’s a dish I’ve been making since Danièle taught it to me more than 30 years ago, and still one of my favorites.

The onions need to caramelize low and slow — which can take a couple of hours, or more. They don’t need much minding, though, just a stir every now and then. Maybe not something you want to tackle on mid-week Pi Day, but doesn’t it sound great for the weekend?

RECIPE: Pissaladière