Wash the rhubarb stalks and slice them into half-inch pieces.
In a small saucepan over medium-low heat, combine the rhubarb, maple syrup, vanilla extract, and a splash of water.
Simmer the rhubarb mixture for 8 to 10 minutes, stirring occasionally, until the fruit has broken down into a thick, jam-like compote, then remove from heat to cool.
In a small skillet over medium heat, melt the coconut oil and add the rolled oats, hemp seeds, cinnamon, and a pinch of sea salt.
Toast the oat mixture for 3 to 5 minutes, stirring constantly, until the seeds are fragrant and the oats are golden brown.
In a glass or bowl, layer half of the Greek yogurt followed by half of the rhubarb compote and half of the toasted crumble.
Repeat the layers with the remaining ingredients and serve immediately while the crumble is still crunchy.