Place the walnuts and sea salt in a food processor and pulse to break the nuts down until crumbly.
Add the tomatoes, spices, and lentils to the processor. Pulse until the mixture is well incorporated. Check for Seasoning, and add additional salt, cumin, or chili as needed. Add a few tablespoons of water, if needed, to bind the mixture together.
Divide the filling into the romaine leaves. Top each with 2 tablespoons of salsa and a few avocado slices. Serve.
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