Winter Sabzi

Name: Winter Sabzi
Ingredients: ⅓ cup canola oil; ½ tsp. brown mustard seed; ½ tsp. cumin seed; 1 medium red onion, finely chopped; 3 medium Roma tomatoes, finely chopped; 1¼ tsp. kosher salt, plus more; ¾ tsp. turmeric; ½ tsp. freshly ground black pepper, plus more; ¼ tsp. red chile powder; ½ lb. parsnips, cut in 1-in. pieces; ½ lb. carrots, cut in 1-in. pieces; 1 russet potato, cut in 1-in. pieces; ½ cup fresh or frozen green peas; Steamed white rice or roti, for serving