I'm in the middle of making David Lebovitz's carnitas. The recipe calls for browning pork chunks and then braising them in the oven uncovered. It's pretty much too late for me to turn back but they are halfway done and they seem brown and tough. I've never braised anything uncovered - is it common? I'm hoping they will soften up towards the end but I'm thinking I should have followed the recipe but covered the pot as in a traditional braise. Thanks.