Preheat your oven to 350°F (175°C) and prepare a greased 9” x 9” baking pan.

In a medium bowl, combine flour, oats, sugar, and a pinch of salt. Cut in cold butter until the mixture resembles coarse crumbs.

Press half of the crumb mixture into the bottom of the prepared baking pan.

Blend softened cream cheese, sugar, and the egg in a stand mixer until smooth. Mix in vanilla, cinnamon, and nutmeg.

Fold in the diced rhubarb, then pour the mixture over the crust and spread evenly.

Sprinkle the remaining crumb mixture over the top of the cream cheese filling.

Bake for approximately 40 minutes, or until the topping is lightly browned and filling is set.

Allow to cool completely on a wire rack, then cut into squares and serve or store.