Take your puff pastry sheets out of the freezer and let them thaw. I usually pull them out and let them sit on the counter for about 30–40 minutes. You want them to be pliable but still cold. If they get too warm, they’ll be sticky, and we don’t want that.
Core and slice them in half. Using a knife or mandoline, slice the apples very thin, like paper-thin. Think delicate flower petals. Place the slices in a microwave-safe bowl with about ½ cup of water and the lemon juice. Microwave for about 3 minutes to soften the slices. This step is important, soft slices roll up beautifully. Hard ones? Not so much. Drain the slices and gently pat them dry with a paper towel.
In a small bowl, melt 2 tablespoons of butter in the microwave. Stir in the sugar and cinnamon until you get a sweet, fragrant paste. Save the other 2 tablespoons of butter for greasing the muffin tin or brushing the tops later (or both!).
Lightly flour your work surface and unfold one sheet at a time. Use a rolling pin to gently stretch it out just a bit, maybe an inch wide,—so you have room to work. Cut each sheet into 6 strips lengthwise. You’ll get 12 strips total from both sheets. Each strip will become one rose.
Spread the cinnamon butter down each strip of pastry. Don’t go crazy, just a thin layer. Lay the apple slices along the top half of the pastry strip, skin side out. They should overlap slightly like petals. Fold the bottom half of the pastry strip up over the bottom of the apple slices. Now you’ve got a little apple sandwich. Roll it up gently but firmly from one end to the other. You’ll see the rose shape appear as you go, so pretty! Place each rolled-up rose into a greased muffin tin.
Preheat your oven to 375°F (190°C). Brush the tops of the roses with the remaining melted butter. You can even sprinkle a little extra cinnamon-sugar if you’re feeling indulgent. Bake for 35 to 40 minutes, until the pastry is golden and cooked through. If the tops start to brown too quickly, just loosely tent the tin with foil.
Let the roses cool for about 10 minutes in the muffin tin, then gently lift them out. Once they’re cool enough to handle, give them a sweet little snowfall of powdered sugar. Totally optional, but highly recommended.
