1. Prepare Oven, Pie Plate, and Rhubarb:

• Preheat oven to 375°F (190°C).
• Take the 1 teaspoon of softened butter and use it to very generously grease the bottom and sides of a 9-inch pie plate.
• Wash, trim, and dice the fresh rhubarb into bite-sized pieces. Place the diced rhubarb directly into the generously buttered pie plate, spreading it out into a relatively even layer. Set aside.

2. Blend the Custard Batter:

• In the container of your blender (or food processor), add the all-purpose flour, granulated sugar, baking powder, salt, large eggs, vanilla extract, and milk.
• Secure the lid. Blend on medium-high speed for 1 or 2 minutes, until the mixture is completely smooth, well-blended, and slightly frothy. Stop and scrape down the sides if needed.

3. Pour Batter Over Rhubarb:

• Carefully pour the blended custard batter evenly over the diced rhubarb in the pie plate.

4. Bake:

• Place the pie plate on the center rack of the preheated oven.
• Bake for 40 minutes at 375°F (190°C).
• The pie is done when the top is golden brown, the edges are puffed, and the center is almost set – it should still have a very slight jiggle when gently nudged.

5. Cool and Set:

• Carefully remove the pie plate from the oven and place it on a wire cooling rack.
• Let the Crustless Rhubarb Custard Pie sit and cool at room temperature for at least 10-15 minutes (or longer) before slicing. The residual heat will finish setting the center as it cools.

6. Serve:

• Slice the pie into wedges directly from the pie plate.
• Serve warm or at room temperature. Enjoy!