Heat the pecan oil and butter in a heavy medium-size skillet over medium heat. Add the onions and cook, stirring often, until they are soft and lightly golden, 8 to 10 minutes. Add the peppers, tomato paste, lemon juice and thyme. Cook, stirring often, for 5 minutes. Remove from the heat and cool.
Transfer the mixture to a food processor. Add the ricotta and Parmesan cheese and process again until smooth. Serve at room temperature or chilled. The mixture can be stored in an airtight container in the refrigerator for up to 1 week. Makes about 11/2 cups