Set oven to 375 F.
Put skillet on a low heat.
Peel the potatoes and slice across the width into 1/4-inch-thick disks keeping the skillet on the burner and leaving the heat on while you start to build the tian. Add a drizzle of olive oil and layer the potatoes. Cover with a lid to slightly steam while you slice the yellow onion.
Peel the onion, then slice into 1/4-inch wide disks and layer on top of potatoes. Drizzle a little olive oil and sprinkle a teaspoon of the herbs. Cover with the lid to steam the onions.
Slice the zucchini into 1/4-inch-thick disks and and layer over the onions. Season with salt and pepper, drizzle with oil and re-cover with the lid. Drizzle a little olive oil and sprinkle the rest of the herbs. Cover with lid to steam zucchini.
Cut the cherry tomatoes in half and arrange as a layer over the zucchini.
Drizzle with oil, season with salt and pepper and top the fisninshed tian with the coarse bread crumbs.
Place in the oven without a cover and bake for 30 minutes.
Serve hot or at room temperature.