First, let's take a look at the macros. Each of these are listed in grams and as usual, normalized to 200 calories for easy comparison, so we're always comparing apples to apples.
| Onions | Tomatoes |
| Nutrient | onions | tomatoes |
| Protein | 6g | 10g |
| Carbohydrate | 47g | 44g |
| Fiber | 9g | 13g |
| Fat | 1g | 2g |
| Monounsat. Fat | 0g | 2g |
| Polyunsat. Fat | 0g | 1g |
| Saturated Fat | 0g | 0g |
Next, let's take a look at the Vitamin density. These values are shown in units of percent of recommended daily intake. And since we're showing 200 calories worth, this means anything above 10% is good.
| Nutrient | onions | tomatoes |
| Choline | 7% | 18% |
| Vitamin A | 0% | 75% |
| Vitamin C | 49% | 188% |
| Vitamin E | 1% | 50% |
| Vitamin K | 3% | 110% |
Tomatoes have significantly more Vitamins A, E, C, K than onions. Onions are a good source of Thiamin, Potassium, Calcium, Phosphorus. Onions are a great source of Vitamin C, Vitamin B6. Tomatoes are a good source of Magnesium, Zinc, Calcium. Tomatoes are a great source of Vitamin A, Vitamin E, Thiamin, Niacin, Vitamin B6, Potassium, Phosphorus, Iron. Tomatoes are an excellent source of Vitamin K, Vitamin C.
And here we see the B-vitamins: B1 (Thiamin), B2 (Riboflavin), B3 (Niacin), B5 (Pantothenic Acid), B6 (Pyridoxine)
| Nutrient | onions | tomatoes |
| Vitamin B1 | 23% | 41% |
| Vitamin B2 | 12% | 19% |
| Vitamin B3 | 5% | 55% |
| Vitamin B5 | 12% | 20% |
| Vitamin B6 | 55% | 81% |
| Vitamin B12 | 0% | 0% |
Now, lets look at mineral density. Here we have a lot of important electrolytes and minerals. Once again, units are in percent of RDI, thus for this 200 calorie serving anything above 10% would considered high.
| Nutrient | onions | tomatoes |
| Sodium | 1% | 4% |
| Potasium | 21% | 75% |
| Calcium | 23% | 22% |
| Magnesium | 14% | 35% |
| Phosphorus | 25% | 46% |
| Iron | 18% | 50% |
| Manganese | 28% | 55% |
| Selenium | 6% | 0% |
| Copper | 20% | 66% |
| Zinc | 9% | 20% |