Step 1

Fill a large pot with lightly salted water and bring to a rolling boil. Stir in the fettuccine, bring back to a boil, and cook pasta over medium heat until cooked through but still firm to the bite, about 8 minutes. Drain and transfer to a serving bowl.

Step 2

Melt butter in a large saucepan over medium heat. Saute mushrooms and sausage in butter until mushrooms are tender and sausage is browned and crumbly, 10 to 12 minutes. Stir spinach into mushroom mixture and cook until heated through, 5 to 10 minutes. Remove from heat.

Step 3

Stir ricotta cheese into mushroom mixture until well-mixed; add lemon juice. Pour mushroom mixture over fettuccine and toss to coat.