Cut steak diagonally across grain into 1/8-inch slices, and place in a shallow dish. Sprinkle with turmeric and chili powder, tossing to coat. Cover and chill 30 minutes.
Pour 1 teaspoon vegetable oil and sesame oil into a nonstick skillet; place over medium-high heat until hot. Add steak; stir-fry until browned. Remove from skillet; set aside.
Pour remaining 1 teaspoon vegetable oil in skillet. Add ginger, garlic, and onion; stir-fry until crisp-tender. Stir in coconut milk; cook, stirring often, 2 to 3 minutes or until slightly thickened.
Stir in steak, cilantro, and red pepper; cook, stirring often, until thoroughly heated.