Vegan Chipotle Lentil Tacos

Make creamy avocado sauce: combine all ingredients in a blender or food processor, and add 2/3 cups cold water. Blend until smooth. Make lentil filling: In a large skillet over medium heat, heat oil. Add onion and cook until soft, 6 minutes. Add garlic and cook until fragrant, 1 minute more. Add tomato paste and chipotle pepper, and cook, mashing pepper with a wooden spoon, until tomato paste has darkened slightly, 2 minutes. Add cumin and coriander and season with salt.  Add lentils and ¼ cup cold water. Stir to combine, then cook, stirring and mashing some of the lentils occasionally, until lentils are heated through and partially mashed, and no liquid remains, about 5 minutes. Add more water a tablespoon at a time if skillet becomes dry. Assemble tacos: fill each tortilla with a big spoonful of lentil mixture, a drizzle of sauce, red onions, and jalapeño.