In a stand mixer fitted with the whisk attachment, whip the cream on medium speed until frothy, 1 to 2 minutes. Gradually increase the speed to high and whip until it’s light and fluffy with stiff peaks, another 2 to 3 minutes. (Don’t overwhip!) Transfer the whipped cream to a bowl.
Replace the bowl on the stand mixer and fit the machine with the paddle attachment (there’s no need to clean the bowl). Place the cream cheese in the bowl and mix on medium until smooth, 2 to 3 minutes. Add the sugar and kosher salt and increase the speed to high. Beat until light and fluffy, 2 to 3 minutes.
Lower the speed to medium and add the food coloring (if using). Add the guava concentrate in four additions, mixing well after each addition, and scraping down the sides of the bowl with a rubber spatula after the second and the final additions. Increase the speed to high and beat until smooth and well incorporated, 1 to 2 minutes. Remove the bowl from stand and, using the spatula, gently fold in the whipped cream in three additions, incorporating completely after each addition.
To assemble, place the passionfruit curd in a pastry bag fitted with a Bismark tip (such as Wilton 230). Fill cooled cupcakes with passionfruit curd. Using an offset spatula, frost with guava frosting. Serve immediately, or keep chilled.