Keto Roasted Vegetable Lasagna
A sophisticated vegetable lasagna built in layers of oven-roasted zucchini, eggplant, mushrooms, and tomatoes, bound together with a silky tomato-sage puree and topped with melted Parmesan. The vegetables are slow-roasted first to concentrate their flavors, then assembled and finished in a hotter oven for a golden crust. Aromatic thyme and sage perfume each component. Serve warm as an elegant vegetarian main course for dinner or special occasions. This version relies on roasting to develop depth rather than traditional cheese béchamel, keeping it lighter and vegetable-forward.
Ingredients
- 2 whole zucchini, trimmed
- 3 whole tomato, cored
- 2 whole eggplant, partially peeled
- 6 whole king oyster mushroomcremini or portobello1:1earthier
medium
- ⅝ oz fresh thyme, leaves chopped, stems separated
- 2 clove garlic, thinly sliced
- 1 ¼ cups Parmesan cheese, finely grated
- 6 tablespoon olive oil
- 2 whole tomato, cored and scored
- 2 whole shallot, trimmed and peeled
- ⅓ oz fresh sage, destemmed
- ¼ teaspoon chili powder
- ¼ teaspoon salt
- ¼ teaspoon ground black pepper
Instructions
- 1
Preheat oven to 275°F in humidity-high mode.
- 2
Peel eggplant partially and cut lengthwise into thin slices.
- 3
Trim zucchini ends and slice lengthwise thinly.
- 4
Slice king oyster mushrooms lengthwise.
- 5
Core tomatoes for lasagna and cut into thick slices.
- 6
Mince garlic thinly. Chop thyme leaves and separate from stems.
- 7
Destem sage and cut leaves into strips.
- 8
Trim shallots, peel, and finely chop.
- 9
Core tomatoes for coulis, score bottoms, and set aside.
- 10
Arrange all sliced vegetables on a baking tray without stacking. Top tomato slices with garlic, sprinkle thyme over remaining vegetables, season with salt and pepper, drizzle with olive oil.
- 11
Roast for 30 minutes on humidity-high mode.
- 12
Meanwhile, boil water and blanch scored tomatoes for 15 seconds, then remove and cool slightly.
- 13
Peel cooled tomatoes, cut into wedges, and puree in blender.
- 14
Stir shallots, sage, salt, and pepper into tomato puree.
- 15
Increase oven temperature to 350°F.
- 16
Layer roasted vegetables in a gratin dish in order: zucchini, mushrooms, tomatoes, eggplant.
- 17
Spread tomato coulis over vegetables and top with Parmesan, pressing gently with a fork.
- 18
Bake at 350°F in convection mode for 25 minutes until golden.
- 19
Garnish with thyme, olive oil drizzle, and chili powder.
Tips
Roast vegetables uncovered in single layer so they caramelize rather than steam; avoid stacking or packing the tray.
Blanch tomatoes only 15 seconds before cooling to preserve structure and prevent mushiness when pureeing.
Press Parmesan gently into coulis with fork so it absorbs liquid and creates a cohesive crust.
Good to Know
Refrigerate covered in an airtight container for up to 4 days. Reheat gently at 160°C for 15-20 minutes to avoid drying.
Roast vegetables up to 2 days ahead; store separately. Prepare coulis 1 day ahead. Assemble and bake on serving day.
Serve warm directly from gratin dish. Pair with a green salad and crusty bread. Suitable for vegetarian dinner parties or meal prep.
Common Mistakes
Overcrowd vegetables on baking tray to avoid steaming instead of roasting.
Blanch tomatoes longer than 15 seconds to prevent mushy puree.
Press Parmesan too firmly into coulis to avoid a hard, impenetrable crust.
Substitutions
Dairy-Free Swaps
General Alternatives
medium
FAQ
Can I make this ahead and freeze it?
Yes. Assemble the complete lasagna, cool fully, wrap tightly, and freeze for up to 2 months. Thaw overnight in the refrigerator before reheating at 160°C for 30-35 minutes covered with foil.
What if I don't have an immersion blender?
Transfer cooled blanched tomatoes to a food processor and puree until smooth. Work in batches if needed. Strain through a fine sieve if a silkier texture is preferred.
Can I use dried herbs instead of fresh?
Use one-third the amount of dried thyme and sage (about 7g thyme, 3g sage total). Add dried herbs early in roasting so they hydrate and release flavor throughout cooking.