The beauty of a Prosciutto and arugula tartine (just a fancy, classic name for an open-faced sandwich) is that it showcases beautiful ingredients in a carefully constructed manner, like artwork. It’s meant to be seen, to be admired, and then devoured. All good things must come to an end.
Preheat the oven to 400 degrees F.
Gently toss the tomatoes with a good drizzle of olive oil. Sprinkle with salt and pepper and scatter the garlic, thyme, and rosemary over the tomatoes. Roast until the tomatoes begin to slump and let off their juices, about 25 minutes. Discard the herb sprigs. Mash the garlic and add to a large bowl. Carefully remove the tomatoes to a plate and scrape the flavored oil into the large bowl.
Mix the ricotta with 1 teaspoon of lemon zest and a pinch of salt in a small bowl.
Add 1 tablespoon oil and the juice of half the lemon (about 1½ tablespoons) to the large bowl. Toss the arugula with the dressing. Season with salt and pepper.
Lightly toast the bread. For each tartine, spread a quarter of the ricotta and drape 2 slices of Prosciutto on top. Top with arugula and roasted tomatoes. Season with salt to taste.