Stir together the apples, sugar, water, cinnamon, and cardamom in a medium pan.
Heat the mixture over medium-high heat to bring it to a simmer, stirring the apples often.
Lower the heat a little to maintain the simmer, then cook the apples for about 5 minutes, stirring a few times - until the mixture has thickened and the apples pieces are a little soft but with a light crunch in the center.
Remove the pan from the heat and allow the apples to cool for 5 minutes. Serve the sauce while it's still warm.