Prepare a muffin tin with cupcake liners. Preheat oven to 400 degrees.
Prepare topping by mixing ingredients together in a small mixing bowl. Place on a baking sheet with parchment paper. Bake in preheated oven for 5 minutes or until toasted.
Add the rhubarb, granular sweetener, cinnamon, and xanthan gum to a saucepan. Heat over medium heat, stirring occasionally, simmer for 3 to 5 minutes, until softened. Allow rhubarb filling to cool.
Add cream cheese and butter to a mixing bowl and beat until creamy. Beat in sweetener, then gently swirl in rhubarb mixture.
Equally divide filling mixture between the 12 muffin tins, top with about 2 teaspoons of topping.
Freeze for about 20 minutes and serve. Freeze in a covered container to store.
Notes
If freezing for more than 30 minutes, you may want to thaw for 3-4 minutes prior to serving.