This recipe calls for roasting the berries to concentrate their flavor and keep fruit intact for a glossy preserve made without pectin. Recipe by Jill Warren Lucas.
4 1/4 to 4 1/2 pounds strawberries (about 3 generous quarts), before trimming
2 tablespoons apple cider vinegar
1 large lemon, zested and juiced
6 cups sugar
2 6-inch sprigs fresh rosemary
1/2 teaspoon unsalted butter
Preheat oven to 325 degrees and set out two rimmed baking pans.
Rinse a quart of strawberries, shake off water and pour onto a clean tea towel to blot dry; choose an older one as it likely will stain. Trim off caps. Keeping small berries whole, cut larger ones in half or thirds so they’re all about the same size. Place on baking pans and repeat with remaining berries.
Roast berries 30 minutes, then stir gently. Return to oven, switching upper pan to lower rack and lower to upper, and roast another 30 minutes.
Remove trays from oven; transfer berries and accumulated juice from one pan to a mixing bowl. Splash a tablespoon of apple cider vinegar onto the empty, still-warm pan. Using a hard spatula, work quickly to loosen any bits stuck to the pan. Add this to bowl with roasted berries. Repeat with second pan.
Add lemon zest and juice, sugar and rosemary sprigs to berries, stirring well to combine. When mixture has cooled to room temperature, stir again, then cover and refrigerate at least 6 hours or overnight.
Boil 6 half-pint canning jars to sterilize; leave in warm water until needed.
Remove mixture from refrigerator and allow to come to room temperature. Transfer to canning pot and add butter. Bring to a boil over medium-high heat. Bubble for 10-15 minutes, stirring often to prevent scorching. Remove from heat when mixture becomes glossy and jammy, or as soon as it reaches 220 degrees on a candy thermometer. If necessary, skim foam.
Remove rosemary sprigs, shaking off any fruity cling, and don’t worry if a few leaves stay behind. Scoop preserves into canning jars, wipe rims clean, then apply lids and screw-on bands. Process 10 minutes in a water bath according to USDA guidelines.