The phrase should read "how dare you" not "how dared you". Even if the betrayal was in the past, you are really talking about your current sense of disbelief and outrage about the betrayal, and would tend to say "how dare you...".
If for some reason you really want to emphasise that the outrage was in the past, and you don't feel that now, "how dared you" is archaic. You might say som