Siem Reap has a well-developed restaurant scene driven by the steady flow of international visitors. The main concentration of places is around Pub Street and the Old Market, but the Wat Bo neighbourhood east of the river and Kandal Village have some better options with less noise.
Khmer food to seek out: fish amok (fish steamed in coconut milk and lemongrass in a banana-leaf cup), beef lok lak (stir-fried beef with lime-and-pepper dipping sauce), and banana blossom salad. Street food around the Old Market is excellent and cheap — fresh spring rolls, grilled corn, and num pang (Cambodian baguette sandwiches, a French colonial legacy).
Cuisine Wat Damnak near Wat Damnak on the east bank is consistently rated among the best restaurants in Cambodia: chef Joannès Rivière serves a changing tasting menu of modern Khmer food using local ingredients. Book well in advance.
Marum on Street 7 is a training restaurant run by the Friends International social enterprise, employing and training street youth. The food is genuinely good, the menu ranges across Southeast Asian dishes, and the staff are attentive.
Mahob on Tep Vong Street focuses on traditional Cambodian recipes with good provenance; less formal than Cuisine Wat Damnak but similarly serious about Khmer cooking.
For cheap and authentic, the food stalls inside and around Phsar Chas (Old Market) and Phsar Leu (Upper Market) are the best options. Most Khmer and Vietnamese noodle soups cost under USD 2.
The Raffles Grand Hotel d'Angkor cafe on Pokambor Avenue is useful for breakfast or a coffee stop in air-conditioned calm; pricey by local standards but the setting in the colonial-era hotel garden is pleasant.