Your heat was too high. I cook my muffins on low heat. The bottoms don't take on color until the latter part of cooking. You need to be patient and cook low and slow so the insides can cook through before the outside gets too brown. It takes up to 15 minutes on each side. If your semolina is getting dark brown or burned, your heat is too high. Wipe out the pan and set your heat a little lower.