Remove stems and ribs from kale. Slice into strips.
Heat a portion of the oil over medium-high heat in a skillet. Add mustard seeds; wait until mustard seeds start popping then add shallots and garlic. Stir for about 1 minute.
Working in batches, add kale and stir every 3 to 5 minutes so that kale gets a decent char. Continue cooking and stirring until all the kale is wilted and charred. Remove kale from the skillet and place in a bowl. Add more oil to the skillet and another batch of kale; repeat process.
Season with lemon juice, salt, black pepper and red pepper flakes.
Nutrition Info per serving: 174 Cals, 10g Fat, 19g Carbs, 4g Dietary Fiber, 6g Protein