Rinse 1 cup long-grain white rice under cold water until the water runs clear, then drain in a fine-mesh sieve.
Heat 2 1/2 cups vegetable broth in a small saucepan until simmering, then keep warm.
Over medium heat, melt 2 tablespoons butter with 1 tablespoon oil in a large skillet with a lid.
Add 1/2 cup orzo to the skillet and stir to coat; sauté, stirring occasionally, until the orzo is golden brown, about 4–5 minutes.
Reduce heat to medium-low and add 1 finely chopped onion; sauté gently until softened, about 4 minutes.
Add 1 clove finely chopped garlic and the drained rice; stir for about 1 minute until the rice looks glossy and slightly translucent.
Pour in the hot broth, then add 1 teaspoon salt and 1/4 teaspoon pepper and bring to a gentle simmer.
Cover, reduce heat to low, and simmer without lifting the lid for 20–25 minutes, until the rice is tender and the liquid is absorbed.
Remove the skillet from heat and let the pilaf sit, covered, for 5–10 minutes; then fluff with a fork.
Stir in 2 teaspoons lemon juice, taste, adjust seasoning if needed, and serve.
