Preheat the oven to 450°F (230°C). Line a baking sheet with aluminum foil.

Combine flour, eggs, and salt in a food processor. Pulse until dough holds together. Knead on a clean surface until smooth and elastic, about 10 minutes. Add water if dough is too dry. Wrap dough in plastic and refrigerate for at least 30 minutes.

Slice pumpkin into 8 pieces. Discard seeds and place on prepared baking sheet. Cover with foil to steam.

Bake pumpkin until tender, about 30 minutes. Remove and let cool.

Heat olive oil in a skillet over medium heat. Add onion and sage. Cook, stirring, until onion is soft and translucent, about 5 minutes. Remove from heat.

Scoop pumpkin flesh and transfer to a mixer. Add onion mixture and cream. Beat until combined. Add egg, salt, and pepper, and beat again. Set aside.

Remove dough from refrigerator and divide into 8 portions. Flatten and pass through pasta roller to desired thickness, forming 8 sheets.

Place one sheet on a floured surface. Drop tablespoons of filling down the length, leaving room to seal. Top with another sheet, press to seal edges, and cut into ravioli shapes. Repeat with remaining sheets.

Bring a large pot of salted water to a boil. Cook ravioli in batches, 3–5 minutes each, until tender yet firm.

Heat butter and sage in a saucepan over medium heat. Simmer and stir until butter is browned and fragrant, 5–10 minutes.