Heat a tablespoon of the olive oil in a pot over medium heat. Add the onion. Sautee the onion for 5-7 minutes, or until it's clear and soft. Add the garlic and cook for 2-3 minutes, stirring frequently, or until the garlic is very fragrant.

Add the split peas and the water to the pot. Bring the water to a boil and reduce to a simmer. Simmer the split peas for 30-35 minutes, or until they're very tender. Most of the water should be absorbed into the split peas, but the mixture should be moist--similar to a thick soup.

Transfer the whole mixture to a food processor fitted with the S blade and add an additional tablespoon of olive oil, the lemon juice, salt, cumin, sumac, and red pepper flakes, if using. Process until the dip retains some of its texture, but is fairly smooth (you can also continue blending until it's totally smooth, if you prefer a uniform texture that's similar to hummus). Add a few splashes of water or another tablespoon of olive oil if desired, to create a thinner dip.

Top the dip with a drizzle of olive oil and any toppings of choice. Serve the dip warm, with pita chips, crackers, or veggies. Dip will keep in an airtight container in the fridge for up to four days.