Dice the tomatoes, shred the cheddar cheese, drain the sliced black olives, and thinly slice the green onions. Set aside.
Add the refried beans to a medium mixing bowl.
Add the chili powder, cumin, salt, and water. Stir until the beans and seasonings are thoroughly combined.
Spread the seasoned refried beans evenly across the bottom of a 9x13-inch casserole dish.
Carefully spread the guacamole over the bean layer, taking care not to mix the two layers together.
Spread the sour cream evenly over the guacamole.
Sprinkle the shredded cheddar cheese across the sour cream.
Finish the 7 Layer Dip with an even layer of diced tomatoes, sliced black olives, and green onions.
Serve immediately with tortilla chips, or cover and refrigerate until you're ready to serve.