Preheat oven to 250 degrees F. Place cherry tomatoes and garlic cloves in a single layer in a 3-quart baking dish (13 x 9) or gratin. Sprinkle with lemon zest.: You will smell a gentle citrus and garlic perfume almost immediately as the dish warms, which signals the beginning of flavor marriage. The visual cue to watch for here is even spacing, the tomatoes should sit without crowding so heat circulates around each one. A common mistake is piling them up, which causes uneven cooking and some tomatoes to burst prematurely. If they are crowded, they will steam rather than gently roast, resulting in less concentrated sweetness.
Pour olive oil into the dish, coming about halfway up the sides of the tomatoes. Season the tomatoes with salt and pepper, and add the herbs to the baking dish. (I like to nestle them between the tomatoes.): The oil should partially surround the cherry tomatoes , carrying heat and flavor into their skins. As the oil settles, it will pick up aromatic oils from the garlic and herbs, scenting the whole pan. You want the salt to dissolve into the surface, so sprinkle it evenly, rather than clumping. Avoid adding too much oil or too little, since too much may dilute the roasted flavors, while too little can lead to uneven cooking or burning at the edges.
Bake, uncovered, for 1-1/2 to 2 hours (cooking time will depend on the size of the cherry tomatoes). When the tomatoes are ready, the tomatoes will be soft, the skins will look wrinkled and will just be starting to burst in areas. Don't cook the tomatoes until they've fully bursted; they should be soft, but not falling apart.: Sensory notes become important during this long roast, you will hear a faint crackle as moisture evaporates and see the skins tighten and wrinkle, concentrating the tomato flesh. The scent transitions from fresh to gently sweet and roasted. The reason for stopping before all tomatoes burst is to retain texture, so you keep delightful little pockets of juice rather than a puddle. Overcooking makes the mixture too loose and can lead to a mushy final product, so resist the urge to continue until everything looks collapsed.
Cool tomatoes in the pan at room temperature, then place in airtight jars. Pour enough of the cooking oil over the tomatoes to submerge by 1/4 to 1/2 inch. Store, refrigerated for up to 5 days. This recipe is not suitable for freezing or canning.: As the pan cools, the oil firms slightly and flavors meld more; you will notice the aroma mellow into a harmonious blend of roasted tomato and herb. Filling jars when the tomatoes are warm helps them settle and allows the oil to creep into crevices, but ensure they are cooled enough to avoid condensation in the jar. A common pitfall is not covering the tomatoes sufficiently with oil, which can lead to faster spoilage. Also, never attempt long term canning with this method, as the preservation technique here is refrigeration only.