Step 1 Cook pasta according to packet instructions.
Step 2 Meanwhile, preheat grill to high. Place pumpkin into a shallow, microwave-proof dish with 2 tablespoons water and cover loosely. Microwave on HIGH for 2–3 minutes, until just tender. Drain.
Step 3 Line a baking tray with baking paper. Arrange pumpkin on tray, spray with oil, then grill for 2–3 minutes, until golden.
Step 4 Drain pasta, then return to saucepan. Add pumpkin, ricotta, pine nuts, sage, oil and pesto. Toss until well combined. Season to taste and serve immediately.