Preheat the oven to 400˚F.
Heat 2-3 tablespoons of olive oil in a large skillet over medium heat. Add the onions, garlic cloves, bay leaf, rosemary sprigs and salt Cook, partially covered at first, stirring occasionally until the onions become translucent. Remove cover and continue cooking until the onions are golden and creamy, about 40-45 minutes.
Remove garlic, bay leaf and discard. Stir in thyme and pepper. (Onions can be made a day ahead and refrigerated until ready to assemble the tart,) While the onions are cooking, fill the tart pan with the prepared pastry. Line the pastry with parchment or foil and fill with pie weights or dried beans.
Bake for 15 minutes, remove weights and paper. Prick the bottom with a fork and return to over for 8-10 minutes until lightly golden. Remove and set aside Assemble the tart: Spread the onions into the pastry. Arrange the salmon and olives over the onions drizzle with 1 tablespoon olive oil and bake 10-15 minutes until bubbling and hot.
Cold smoked salmon blended with an assortment of fresh herbs placed in a homemade pastry crust.