Red Pepper Jelly
Add peppers to food processor and pulse until finely chopped but not pureed.
Peel and core apple, but do not discard peel and core. Enclose peel and core in cheesecloth bundle tied with butchers twine. Set aside.
Dice flesh of apple. Place in heavy-bottomed medium saucepan, along with peppers, sugar, vinegar, red pepper flakes, salt and the reserved cheesecloth bag containing peel and core. Bring saucepan to a boil over high heat, then reduce heat to medium-low. Simmer gently, stirring often 45 to 50 min., or until liquid has reduced by about 2/3rds. (Watch carefully to avoid scorching, reduce heat if mixture begins to stick to bottom of pan.) To check for correct thickness, drop a spoonful if mixture onto a chilled plate -- it should hold a trail when your finger is dragged through.
Remove and discard cheesecloth bag. Pour hot jelly mixture into three 1-cup (250-mL) or six 1/2-cup (125-mL) canning jars. Apply sealing lids and screw on tops. Let stand for 24 hr. undisturbed at room temperature. Place in refrigerator. Keeps well, chilled, up to 3 weeks.