Stir all the dry mix ingredients together and keep in an airtight jar.
To make the sauce, whisk the dry mix with the tomato paste, water, and vinegars (and lemon juice, if using) in a small saucepan over medium heat until smooth.
Bring to a gentle boil and keep whisking for 3–4 minutes, until slightly thicker.
Take off the heat, let cool completely, then chill in a closed jar.
Notes
Dry mix keeps up to 6 months in an airtight jar. Prepared sauce: refrigerate in a sealed jar for about 1–2 months.