In medium bowl toss lamb cubes with 1 tablespoon of curry powder and set aside.
Heat butter and olive oil in heavy skillet and add lamb cubes. Brown on all sides, about 4 minutes, remove from heat and move to a 4-6 quart crock pot. Add onions and remaining 1 tablespoon curry powder to skillet; cook and stir until onions are crisp tender.
Stir in flour and cook and stir until bubbly. Add 2 cups water and stir until thickened. Pour this mixture into slow cooker.
Add the remaining ingredients except coconut milk, lemon juice and rice.
Cover and cook on low for 8 to 9 hours until all ingredients are tender. Stir in coconut milk and lemon juice and serve over hot cooked rice.