STRAWBERRY: This works really well in between layers of cake.

If using fresh berries, chop or cut into pieces. If using frozen berries, allow them to soften just a bit, then pulse a few times in food processor, blender, or magic bullet. If you have a stick blender you can blend during or at the end of the cooking process.

In a small sauce pan, add your chopped berries, and optional 2 to 3 TB of water.
Simmer on low to medium-low (depends on your stove) until the fruit has completely cooked down.
As it cooks the fruit will break down and you should be able to stir it to finish the "blending" process. Otherwise you can use your stick blender or food processor.
Add honey, agave nectar, or other desired sweetener, roughly 1/4 cup. More if you like it sweeter.

Allow to cool.

RHUBARB:
Chop rhubarb into approximate 1-inch chunks.
Place in large sauce pan with up to 1/4 cup of water.
Simmer on low for about 30 to 60 minutes, until rhubarb has completely cooked and broken down into a sauce.
Add sweetener of your choice.

Serve warm or cool over cake, yogurt, or ice cream.