Slice the pluots in half, lengthwise, then twist to open and remove the pit. Set aside.
In a small bowl whisk together the water, cinnamon and marmalade until well blended, then brush the mixture onto each pluot half. Place the pluots, flesh side down, on the hot grill and cook for 3 to 4 minutes, brushing occasionally with more marmalade. Turn the pluots skin side down, brush the flesh with marmalade and grill 2 more minutes until tender and caramelized. Remove from the heat, place the grilled pluots on a dessert plate, top with ice cream and sprinkle with granola.
You may want to grill extra fruit, since chopped pluots mixed with yogurt and a drizzle of marmalade are a delicious breakfast treat. Or dice them into a summer fruit salsa, with sweet onions and fresh chilies, and serve with chicken or flaky white fish.