Given a paragraph about cooking, and a set of conversational question answers about the paragraph, generate a relevant question to the topic of the paragraph. The paragraph has the prefix 'CONTEXT:'. Each conversation question has a prefix `Q:` followed by the answer prefix `A:`.

Q: CONTEXT: It might be there for body, but more likely for the umami kick that tomato past helps with. I bet you could leave it out with no ill effect...otherwise, try some ketchup. You could also open the small can, use what you need and put the rest in a baggy in the freezer.  <sep>  Q: What can I substitute for tomato paste to thicken a marinade? A: try some ketchup  Q: Why ketchup? A: It might be there for body, but more likely for the umami kick that tomato past helps with 

A: How much ketchup should I use to substitute if I need 2 TB of tomato paste?
****
Q: CONTEXT: In the fridge, an hour should not be a problem, but could still end up bitter depending on the kind of onion used. Usually, Marinades, Pestos etc. that use mashed onions and/or garlic taste best if they are made the way the name "Pesto" suggests: Cutting stuff very fine, then using a mortar and pestle. Most explanations WHY that is the case have to with the fact that blenders tend to disintegrate cell walls with relatively rough cuts of a fast but half-sharp or blunt blade, releasing more enzymes etc. from the cell walls as opposed to from the cell contents. These are plausible, since some of the compounds in different parts of onion cells are known to actively react when the onion is disintegrated.Also, try adding oil (which you often want in a marinade anyway. No unrefined olive oil in a blender, though - that is known to get bitter!) while mortaring or blending - this will help extract flavor compounds and probably provide some oxidation protection.There is a well known marinade working with onions, garlic etc: Bulgogi marinade.  <sep>  Q: How long can blended onions stay relatively fresh? A: In the fridge, an hour should not be a problem, but could still end up bitter depending on the kind of onion used 

A: What does TVP stand for?
****
Q: CONTEXT: Sous vide cooking is a function of temperature and the surface area to volume ratio of the food in question.If you have a high surface area to volume the cooking time will be shorter. Steaks would have a higher ratio than the roast so they would take less time than the roast. The amount of the time difference is difficult to predict exactly over such a long time scale, but a rough calculation of the ratio I spoke of would be a good starting point for a compensation factor.If you have the time and your water bath can accommodate, I'd suggest keeping the roast whole and finishing in a skillet. It's much more impressive than a steak.  <sep>  Q: Should I Sous vide chuck roast or chuck steaks? A: Steaks would have a higher ratio than the roast so they would take less time than the roast 

A:
Which would taste better?
****