Wash and drain lentils and bulgur thoroughly. Add lentils to a pot with water and bring to a boil. Once boiling, turn down the heat to medium-low and simmer, covered, for 25-35 minutes. 15 minutes into cooking time, add bulgur, salt, cumin if you like, and 1 tbsp olive oil. At 25 mins, check if the lentils are tender.
Meanwhile, prepare the crispy onions. Chop the onions and add in a saucepan with vegetable oil and 1 tbsp of olive oil. Fry until browned and crispy for 10-15 minutes. Watch closely to make sure they don't burn. Remove onions from oil and dry on a paper towel-lined plate.
Add half of the fried onions to the lentil and bulgur mixture, stirring to infuse flavors and combine.
Prepare yogurt by mixing yogurt, lemon juice, salt, garlic, mint, and water, until smooth. Fold in the cucumber slices.
Top the hot mujadara with the rest of the crispy onions and serve with a side of cool cucumber mint yogurt.