Indian cauliflower and potato (aloo gobi)

This recipe is from a wonderful and easy-to-follow cookbook, Healthy Indian Vegetarian Cooking by Shubha Ramineni. Using a large skillet (or a low-walled Dutch oven), heat 3 Tbsp vegetable oil, then add 1 medium vine-ripe tomato (quartered).  Cover the skillet and cook until tomato becomes soft, stirring frequently.  Add 1 medium head cauliflower (washed and cut into small florets), 1 medium russet potato or two small Yukon potatoes (peeled and cubed), 2 tsp microplaned fresh ginger, ½ tsp turmeric, ¼ tsp cayenne pepper, 1 ½ tsp salt, and ¼ tsp black pepper (we sometimes also add a handful of curry leaves).  Stir to combine until everything is stained yellow.  Increase the heat to medium-high, and cook covered for 7 mins, stirring occasionally.  Remove the cover (to avoid cauliflower getting mushy) and reduce heat to medium, cooking until cauliflower and potato are cooked through (about 10 mins).  Turn off the heat, cover, and let sit for 5 mins.  We added several fresh curry leaves (Mar. 2015)