Rhubarb Swirl: In saucepan, cook rhubarb & sugar over medium heat, stirring, until rhubarb is broken down and mixture is thick and glossy, 10 - 15 minutes. Scrape into bowl. Let cool to room temperature.

Cream Cheese Swirl:

Meanwhile, in bowl, beat cream cheese with sugar

until smooth. Beat in egg yolk and cornstarch. Set aside.

Brownies:

In saucepan, melt chocolate and butter over

medium heat, stirring occasionally, until smooth. Remove from heat. Let cool for 10 minutes. Whisk in sugar & vanilla; whisk in eggs, 1 at a time. Stir in flour and salt. Scrape into parchment paper-lined 9 inch square cake pan.

Alternately spoon rhubarb swirl & cream cheese swirl over top; using butter knife, gently swirl to create marble effect. Bake in 350F oven until cake tester inserted in centre comes out clean with a few moist crumbs clinging, 40 to 45 minutes. Let cool completely in pan.