This delicious jam recipe is courtesy of Gretchen Sweet, Martha's friend from Maine.
- 2 1/4 pounds fresh or frozen (partially thawed) raspberries
- 3 3/4 cups granulated sugar
- Juice of 1 small lemon
Place 5 clean 8-ounce jars right side up on a rack in a boiling-water canner. Fill the canner and jars with hot water, about 1 inch above the tops of jars. Boil jars over high heat for 10 minutes. Remove and drain hot sterilized jars one at a time, reserving hot water for processing filled jars. Place jars on a wire rack set over a rimmed baking sheet.
In a large saucepan filled with water, bring to a boil over high heat and reduce to a simmer, add clean lids and lid rings. Simmer for 10 minutes; do not boil, as this may cause problems in sealing jars. Drain lids and rings; set aside.
Combine all ingredients in a medium saucepan and bring to a boil over high heat. Cook, stirring and skimming foam from surface, until mixture reaches 221 degrees on a candy thermometer, 5 to 10 minutes. To test, remove mixture from heat. Pour a small amount of jam on a cold plate and transfer to freezer, for 2 to 3 minutes. If mixture gels, it is ready to fill. If not, return to heat and retest.
Fit a jar with a wide-mouth funnel. Ladle jam mixture into jar up to the fill line. Repeat process with remaining jars. Put lids and rings on jars and tighten; do not over-tighten. At this point, jam may be kept refrigerated, up to 1 month.
To store jars at room temperature for up to one year, reheat water in the canner until it reaches at least 180 degrees, within 10 minutes of filling the jars. Place filled jars into the canner one at a time, using a jar lifter that is securely positioned below the neck of the jar. Keep jars upright at all times.
Add more boiling water, if needed, so that water covers jars by at least 1 inch. Increase heat to high and cover. Once water begins boiling, heat jars for 5 minutes. Turn off heat and gently transfer jars to a wire rack set over a rimmed baking sheet and invert, spacing each jar at least 1 inch apart. Avoid placing jars on a cold surface or near a cold draft.
Let jars sit undisturbed until fully cooled, 12 to 24 hours. Do not tighten ring bands on the lids or push down on the center of the flat metal lid until jar has cooled completely.
Once jars have cooled completely, test to make sure each jar is completely sealed. Press down on the middle of the lid with a finger. If lid springs up when finger is released, the jar is unsealed. Store sealed jars in a cool place for up to one year. If any of the jars are unsealed, store in the refrigerator and use within several days. Always refrigerate jam after opening.