In a saucepan, combine the cranberries, sugar and orange juice/water.
Bring to a boil over medium heat, then simmer for about 20 minutes on medium-low heat, stirring frequently. The cranberries should all burst, and the mixture will be thick.
Use a blender, immersion blender or food processor to briefly puree the fruit and break down the pulp. No need to try to get it really smooth, since you'll be straining out the seeds and pulp.
Set a fine mesh strainer over a bowl. Pour the cranberries into the strainer, then use a silicone spatula to press the liquid through the strainer. Press as much through as you can, then discard the seeds and pulp left in the strainer.
Refrigerate the jelly in a lidded jar or container until completely cooled.
Notes
Homemade cranberry jelly should be refrigerated for up to 2 weeks, or frozen for up to 3-6 months.