Preserve Recipe

Toast nuts

In a small dry skillet over medium heat, toast the pine nuts (or walnuts) until fragrant and lightly golden, about 3–5 minutes, shaking the pan frequently. Remove from heat and let cool.

In a food processor, combine basil, parsley, cooled toasted nuts, grated Parmesan, and garlic. Pulse until coarsely chopped.

With the processor running, stream in the 1/2 cup olive oil until the mixture becomes a loose paste. Scrape down the sides as needed.

Add lemon juice, 1 tsp salt, and 1/2 tsp black pepper. Pulse to combine and taste; adjust salt, pepper, or lemon as desired. Transfer pesto to a bowl and set aside. (If making ahead, cover and refrigerate.)

Heat a wide skillet over medium-low heat. Add butter and 1 tablespoon olive oil until butter melts and foams.

Add the thinly sliced onions and 1/2 tsp salt. Stir to coat. Cook slowly, stirring every 3–5 minutes, so the onions soften and brown slowly. This takes about 25–35 minutes.

If onions begin to stick or dry out, add a splash (1–2 tbs) water. For sweeter, faster caramelization you may sprinkle 1 tsp brown sugar after 10–15 minutes.

When onions are deeply golden and jammy (25–35 minutes), stir in 1 tablespoon balsamic vinegar if using and cook another 1–2 minutes to deglaze. Remove from heat and let cool slightly.

Preheat oven to 375°F (190°C) if you prefer roasted tomatoes; alternatively you can confit them on the stovetop.

Roast method (recommended)

Halve the roma tomatoes lengthwise and place cut-side up on a baking sheet. Scatter the thinly sliced garlic over them, drizzle with 2 tablespoons olive oil, and season with 3/4 tsp salt, 1/4 tsp black pepper, and red pepper flakes if using. Roast 25–30 minutes until tomatoes are soft, slightly caramelized at edges, and garlic is mellow.

Stovetop confit method

In a small skillet over low heat, combine tomatoes (halved or quartered if large), sliced garlic, and 2 tbs olive oil. Season with salt, pepper, and red pepper flakes. Cook gently, stirring occasionally, until tomatoes collapse and garlic is soft, about 15–20 minutes.

Let tomatoes and garlic cool slightly. Roughly chop roasted tomatoes if desired for easier jar layering. Reserve any pan juices — they add flavor to the preserve.

Sterilize jars: If not already done, wash jars and lids in hot soapy water and either simmer in boiling water for 10 minutes or run through a hot dishwasher cycle. Keep hot until ready to fill.

Layering: Spoon a thin layer (about 1–2 tbsp) of pesto into the bottom of each jar to create a flavor base. Next add a generous layer of caramelized onions (about 2–3 tbsp per 8 oz jar). Add roasted tomatoes and garlic with some of their juices (about 3–4 tbsp). Repeat if jar size allows, finishing with a small spoonful of pesto on top for extra aroma.

Add oil and herbs: Pour just enough extra-virgin olive oil into each jar to cover the contents and create an oil cap (this helps preservation and flavor). Nest a couple of basil leaves into the oil if desired.

Seal & store: Wipe rims clean, place lids on jars, and refrigerate. For short-term use, refrigerate and use within 2 weeks. For slightly longer storage (up to 1 month) keep submerged in oil and always use a clean utensil to remove portions. This recipe is not hot-water processed for long-term shelf stability.

Serving suggestions: Serve the preserve at room temperature as a spread on crostini, stirred into pasta, spread on sandwiches, or spooned over grilled fish or chicken.