Heat 2 1/2 cups water, the butter and cardamom in a medium saucepan over medium heat just to a simmer. Add the peaches, reduce the heat to low and cook until the peaches are very tender but not falling apart, 25 to 30 minutes. Cool in the liquid about 15 minutes and then drain and cool the fruit to room temperature. (This can also be done a couple hours ahead and the peaches can be left in the liquid until ready to assemble.)
Blend the goat's cheese with the cream, honey and orange zest in a small bowl.
To assemble, pat the peaches dry with paper towels if very wet and place 6 on a large serving plate. Top each peach with some of the cheese mixture, a sprinkle of pistachios and another peach, followed by more cheese and pistachios and a third peach. Garnish each napoleon with a drizzle of honey, some more pistachios and a light sprinkling of orange zest and sea salt, if using.