Blend ingredients for the shells, adding the coconut oil last.
Grease each tart pan or mold with coconut oil and dust with almond flour. Press the tart mixture in, using a glass bottom to flatten.
Baked: I baked mine 15 min at 325 degrees F, just to brown the top edges and create a more pie-crust-like crumbly texture.
No-Bake: Just press the raw tart mixture in, and put them directly into the freezer for about an hour. The edges will be lighter, and the texture more chewy.
Make the Raspberry-Rhubarb syrup
Rinse and chop the rhubarb into 1-inch bits and put into a medium sauce pan. Cover the rhubarb with water, and bring to a boil. Reduce heat and simmer for about 20 minutes. Use a spoon to keep clearing the debris that rises to the top.
In the last 5 minutes, add in the raspberries and mush with a fork or potato masher.Remove from heat, strain the liquid (it's pink!). Compost the fruit; it's lost flavor and nutrition.
Rinse the pan, return the pink liquid to it and add in the sugar. Let the liquid bubble for about 5 minutes or until the sugar is dissolved.
Remove from heat, stir in the lemon juice, and let syrup cool. You can taste test as soon as it is cool enough. Some people prefer it sweeter. If you want, you can return it to the stove, add in another ¼ cup of sugar and simmer again for 5 minutes. This will also thicken it to become more of a syrup suitable for pancakes and waffles.
Whether you add additional sugar or not, strain the pink liquid one more time, let it cool to at least warm, and store in refrigerator for 2 weeks, although watch the surface for any mold growth.
Make the tart filling
Stir the cooled syrup into the yogurt.
Present the tarts
Fill the tarts with yogurt. I topped mine with coconut sugar, and fruit! Keep refrigerated until ready to serve.