Place cauliflower florets in a steamer basket over boiling water, cover and steam until very tender, 12 to 15 minutes. (Alternatively, place florets in a microwave-safe bowl with 1/4 cup water, cover and microwave on High for 3 to 5 minutes.) Place the cooked cauliflower in a food processor and blend until very smooth.
In a mixing bowl, combine the cauliflower, pumpkin, Swerve, eggs, almond milk, salt, 1/3 cup butter and vanilla. Mix together and pour into a greased 13x9 inch baking dish.
To prepare the topping, combine the Swerve, almond flour, 1/3 cup melted butter and pecans. Mix together and crumble over "sweet potato" mixture. Bake uncovered at 350 degrees F (175 degrees C) for 35 to 45 minutes.