In this guide, I want to help you solve the issue of why your macarons have cracked tops. I'll teach you the top issues related to equipment, technique, and ingredients that could be leading to cracked shells.
If you have cracked macarons only around the outside perimeter of your baking sheet, you're likely experiencing oven hot spots. Oven hot spots happen because many ovens (especially conventional home ovens) don't evenly disperse heat.
Another common issue related to cracked macaron shells is over macaronaging. Macaronage is a term that refers to folding the dry macaron ingredients (almond flour and confectioners' sugar) into the meringue. This process smooths the mixture and helps the macarons bake with proper structure.
Did you put your macarons in the oven without banging them on the counter? This could be the reason your macarons cracked. Oftentimes, air bubbles are trapped in the macaron batter. Air bubbles occur naturally in the batter during the macaronage and piping process.
It's important to allow your macarons (no matter what style of meringue you made) to rest on the counter until they've formed a skin. Typically, you'll need to allow the shells to rest for about 45 - 60+ minutes on the counter until a skin has formed on top. If you live in a humid climate, this may take up to 90+ minutes.
Food coloring also adds additional moisture to your macarons. Typically, if you're using gel food coloring or powdered food coloring, this isn't going to be an issue for you. However, liquid food coloring may be causing cracking on your macarons.