A discussion on microwave cooking on another board (The Modern "Microwave" Oven, NAF) prompted me to post this simple recipe that I use all winter for instant, delicious marmalades from the microwave oven.
Because it is so easy and quick, I only make small batches and have no idea how this would work for pounds of fruit.
I choose one large piece of citrus fruit or two small ones - orange, lemon, tangerine, lime, etc. Wash it well and cut into chunks, skin and all. Remove all seeds & coarsly chop.
NOTE: for grapefruit, I discard the white pith as it can be extremely bitter.
Measure fruit and add equal amount of sugar to 8 C Pyrex measuring cup or similar size bowl. Stir to blend. Cook on 100% power approx 8 minutes, stirring occasionally. Cook until thickened. Pour into jam jar, cover and refrigerate.
I don't cover this while cooking, although I suppose you could. I tried this using apples once figuring that their high pectin level might work well also but got some too-sweet sort of applesauce instead. Have stuck to marmalade ever since.