Preheat oven to 350°.

Rhubarb Honey Jam

In a large saucepan over medium-high heat, add the chopped rhubarb, 1/4 cup granulated sugar, 1/4 teaspoon salt and 2 Tablespoons water for the rhubarb honey jam. Cook, stirring occasionally for about 10 minutes, or until the rhubarb is cooked down and the sauce has thickened.

Remove from the heat. Stir in the honey and vanilla extract and set aside to cool.

Cupcakes

Meanwhile, in a large bowl, beat the butter and sugar until smooth. Add the egg, vanilla extract, milk and sour cream and blend until smooth.

Add the dry ingredients to the bowl and beat slowly until well combined and only a few lumps remain.

In lined cupcake pans, fill each cup ¾ full. Bake at 350° for 25 minutes, or until a toothpick inserted in the center of the cupcake comes out clean. Set aside and allow to cool completely.

Buttercream

Add 1/2 cup rhubarb sauce to a large bowl along with 1 stick butter. Beat with a mixer until smooth. Mix in the vanilla extract and slowly add in the powdered sugar, 1 cup at a time. When all the powdered sugar is incorporated, beat on high until the buttercream is light and airy.

Add the buttercream to a piping bag with a piping tip.

Cupcake Assembly

After your cupcakes and rhubarb honey jam are cooled to room temperature it's time to fill them. Scoop about 1 Tablespoon out of the center of each cupcake. Fill with two teaspoons of rhubarb jam and cover the with the piece of cupcake that you removed.

Pipe a swirl of buttercream on top of each cupcake. Store in an airtight container.