Combine all dough ingredients except melted butter in the bowl of a stand mixer fitted with a dough hook. With the mixer on low speed, slowly add 2 Tablespoons melted butter. Increase speed to medium and mix until a shaggy dough forms.
Transfer the dough to a smooth work surface and knead by hand until a smooth, slightly tacky dough forms; add more milk or flour 1 Tablespoon at a time if needed.
Place dough in a large greased bowl, cover with plastic wrap, and let rise 60-90 minutes until doubled.
While dough rises, melt 1 Tablespoon butter in a small skillet over medium heat. Add diced apples and cook until softened, about 3-4 minutes. Remove from heat and stir in lemon juice; set aside.
Grease a 9x5-inch loaf pan and set aside. In a small bowl, combine brown sugar, cinnamon, and nutmeg; mix well.
After dough has risen, turn onto work surface and divide into 10 roughly equal pieces. Flatten each into a 4-inch oval.
Spread each oval with softened butter, sprinkle with brown sugar mixture, and add apples to half the oval.
Fold each piece in half (like a taco) and place fold-side down in the prepared loaf pan. Repeat until pan is filled.
Cover loaf with plastic wrap and let rise another 30-45 minutes until puffed.
Preheat oven to 350℉.
Bake for 15 minutes, then tent with aluminum foil and bake another 20-25 minutes until golden brown and internal temperature reaches 200℉.
Cool loaf in pan 10 minutes, then transfer to a rack to cool completely.
To make glaze, whisk powdered sugar, vanilla extract, and milk until smooth.
Drizzle glaze over the cooled bread before serving.