Prepare the raspberry sauce first so that it has time to cool before swirling over cheesecake.
In a small saucepan over medium heat, combine raspberries, sugar, and water.
Increase heat to medium-high and stir frequently, about 8-10 minutes (until raspberries have released their juices and the mixture has reduced some).
Remove from heat and press mixture through a fine mesh strainer into a heat-proof bowl. Set aside and allow to cool (discard leftover seeds and fruit pieces).
Preheat oven to 325F.
Prepare brownie batter according to Best Ever Brownies instructions (or package instructions, if using box-mix).
Spread evenly into the bottom of a greased and floured 9x13 pan (alternatively, line the pan with foil and then lightly spray with cooking spray -- this will make it easy to lift the brownie/cheesecake out of the pan and make clean cuts once its cooled).
Bake on 325F for 20 minutes, or until center is almost set (it should not still be liquid, and the edges will appear somewhat cooked).
As the brownie layer bakes, prepare your cheesecake.
In a stand mixer (or in a large bowl with a hand-mixer), beat together softened cream cheese and sugar, scraping down the sides with a spatula occasionally to ensure it is mixed well. (beat on medium-speed about 1-2 minutes, scraping down side occasionally, it should be creamy and well-mixed).
Add sour cream, mix well, stopping once to scrape down the sides before mixing again.
Add eggs, one at a time, beating until just mixed after each addition (and scraping down the sides after each addition).
Stir in vanilla extract.
Once brownie layer has finished baking (do not turn off your oven), evenly spread the cheesecake over the brownie layer.
Take your raspberry sauce and use a spoon to place large droplets (about the size of a dime to the size of a nickel) all over the top of the cheesecake layer.
Use the point of a toothpick to swirl the raspberry across the top of the cheesecake.
Bake on 325F for 40 minutes, or until center is set (not liquidy, bounces back to the touch).
Allow to cool to room temperature, and then place in refrigerator for at least 6 hours before cutting and serving.