The crust is simple... two cups flour, 1 1/2 sticks butter, pinch of kosher salt, about half a cup of sugar, and enough milk to grab it all together once you've got all the fat incorporated into the flour/sugar. I also toss in about 4oz cream cheese, because it seems to help the crust withstand the 'innards' better later on. Chill it, roll it, and blind-bake it in a 375 oven for about fifteen to twenty minutes, weighted down with something to keep it in one place. I used marbles over aluminum foil, but you can do whatever. Just try not to burn your self. It takes all the fun out of the 'baking experience'.
Meanwhile, you can also be cooking your rhubarb. You'll need about three cups for two tarts. Chunk it up, place it, a cup of sugar, and 1/4 to 1/3 cup of water in a baking dish, cover, and bake in a 350 oven for about 40-50 minutes, less if your rhubarb is of new shoots. Let it cool, and drain the juices off. I add a bit more sugar to the juices (1/4 to 1/3 cup) and simmer to reduce to a fairly sticky syrup. This has to cool, too.
In a mixer, combine 12 to 16 ounces cream cheese (my chirruns handicapped me and this time I had only a brick and a half to work with), softened, with about 1/2 cup powdered sugar, 1/2 cup white sugar, and 1 Tbsp. Triple Sec (or Grand Marnier/Cointreau/lemon vodka... heck, white rum will do also, but add a bit of lemon or orange zest if Captain Morgan is the one helping in the kitchen). Beat this mixture well, and slowly add in a few Tbsp heavy whipping cream to thin it a bit. More sugar may be required... this is all sweeten to taste, but more can't hurt, as the rhubarb is so tangy. Chill this mixture until you are ready to assemble all the elements together...
it's pretty self-explanatory from here. Try not to get it on your chin.