I also do an apple dessert pizza, somewhat similar to what you are doing but I make a cheese custard that goes on first. I soak the apples in lemon juice (skin on), while the apples are soaking I brush a skin with melted butter then add a liberal amount of cinnamon and a sprinkling of sugar, then I apply a layer of the cheese custard followed by the apple slices, to top the pizzas I either apply a streusel topping or just sprinkle generously with raw sugar.
When finished wit raw sugar the pizzas are served "as is" either hot or cold but when topped with the streusel I always finish the pizza after about 5-minutes of cooling with a generous drizzle of powdered sugar icing. To make the cheese custard I blend 16-ounces of cream cheese and 8-ounces of powdered sugar until smooth, then add 2-whole eggs and mix smooth, then 16-ounces of sour cream and 16-ounces of ricotta cheese and blend until smooth. If the mixture needs to be thinned for better spreading viscosity add a little cream until I get a good, spreadable consistency. Unused custard will keep for up to a week in the refrigerator. Note: Half size batches are better sized for home use. Spread the cheese custard over the prepared skin about 3/16-inch thick keeping it about 1/2 -inch away from the edge. In addition to apples I also use banana, berries, peaches, mango, kiwi, grapes, dates (date season in California) and even occasionally toss on a few chopped pecans.
Tom Lehmann/The Dough Doctor